Journal articles: 'TWP-ICE'

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Klein, Marco, Moritz Hartmann, and Franz von Bock und von Bock und Polach. "Note on the Application of Transient Wave Packets for Wave–Ice Interaction Experiments." Water 13, no. 12 (June 19, 2021): 1699. http://dx.doi.org/10.3390/w13121699.

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This paper presents the transient wave packet (TWP) technique as an efficient method for wave–ice interaction experiments. TWPs are deterministic wave groups, where both the amplitude spectrum and the associated phases are tailor-made and manipulated, being well established for efficient wave–structure interaction experiments. One major benefit of TWPs is the possibility to determine the response amplitude operator (RAO) of a structure in a single test run compared to the classical approach by investigating regular waves of different wave lengths. Thus, applying TWPs for wave–ice interaction offers the determination of the RAO of the ice at specific locations. In this context, the determination of RAO means that the ice characteristics in terms of wave damping over a wide frequency range are obtained. Besides this, the wave dispersion of the underlying wave components of the TWP can be additionally investigated between the specific locations with the same single test run. For the purpose of this study, experiments in an ice tank, capable of generating tailored waves, were performed with a solid ice sheet. Besides the generation of one TWP, regular waves of different wave lengths were generated as a reference to validate the TWP results for specific wave periods. It is shown that the TWP technique is not only applicable for wave–ice interaction investigations, but is also an efficient alternative to investigations with regular waves.

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Zeng, Xiping, Wei-Kuo Tao, Scott W. Powell, Robert A. Houze, Paul Ciesielski, Nick Guy, Harold Pierce, and Toshihisa Matsui. "A Comparison of the Water Budgets between Clouds from AMMA and TWP-ICE." Journal of the Atmospheric Sciences 70, no. 2 (February 1, 2013): 487–503. http://dx.doi.org/10.1175/jas-d-12-050.1.

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Abstract Two field campaigns, the African Monsoon Multidisciplinary Analysis (AMMA) and the Tropical Warm Pool–International Cloud Experiment (TWP-ICE), took place in 2006 near Niamey, Niger, and Darwin, Northern Territory, Australia, providing extensive observations of mesoscale convective systems (MCSs) near a desert and a tropical coast, respectively. Under the constraint of their observations, three-dimensional cloud-resolving model simulations are carried out and presented in this paper to replicate the basic characteristics of the observed MCSs. All of the modeled MCSs exhibit a distinct structure having deep convective clouds accompanied by stratiform and anvil clouds. In contrast to the approximately 100-km-scale MCSs observed in TWP-ICE, the MCSs in AMMA have been successfully simulated with a scale of about 400 km. These modeled AMMA and TWP-ICE MCSs offer an opportunity to understand the structure and mechanism of MCSs. Comparing the water budgets between AMMA and TWP-ICE MCSs suggests that TWP-ICE convective clouds have stronger ascent while the mesoscale ascent outside convective clouds in AMMA is stronger. A case comparison, with the aid of sensitivity experiments, also suggests that vertical wind shear and ice crystal (or dust aerosol) concentration can significantly impact stratiform and anvil clouds (e.g., their areas) in MCSs. In addition, the obtained water budgets quantitatively describe the transport of water between convective, stratiform, and anvil regions as well as water sources/sinks from microphysical processes, providing information that can be used to help determine parameters in the convective and cloud parameterizations in general circulation models (GCMs).

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Frederick, Kaycee, and Courtney Schumacher. "Anvil Characteristics as Seen by C-POL during the Tropical Warm Pool International Cloud Experiment (TWP-ICE)." Monthly Weather Review 136, no. 1 (January 1, 2008): 206–22. http://dx.doi.org/10.1175/2007mwr2068.1.

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Abstract The Tropical Pacific Warm Pool International Cloud Experiment (TWP-ICE) took place in Darwin, Australia, in early 2006. C-band radar data were used to characterize tropical anvil (i.e., thick, nonprecipitating cloud associated with deep convection) areal coverage, height, and thickness during the monthlong field campaign. The morphology, evolution, and longevity of the anvil were analyzed, as was the relationship of the anvil to the rest of the precipitating system. The anvil was separated into mixed (i.e., echo base below 6 km) and ice-only categories. The average areal coverage for each anvil type was between 4% and 5% of the radar grid. Ice anvil thickness averaged 2.8 km and mixed anvil thickness averaged 6.7 km. Areal peaks show that mixed anvil typically formed out of the stratiform rain region. Peak production in ice anvil usually followed the mixed anvil peak by 1–3 h. Anvil typically lasted 4–10 h after the initial convective rain area peak. TWP-ICE experienced three distinct regimes: an active monsoon, a dry monsoon, and a break period. During the experiment (except the active monsoon period) there was a strong negative correlation between ice anvil thickness and ice anvil height, a strong positive correlation between ice anvil area and thickness, and a greater variance in ice anvil bottom than ice anvil top. These results have important implications for understanding how anvil affects the tropical atmosphere.

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Um, J., G. M. McFarquhar, Y. P. Hong, S. S. Lee, C. H. Jung, R. P. Lawson, and Q. Mo. "Dimensions and aspect ratios of natural ice crystals." Atmospheric Chemistry and Physics Discussions 14, no. 22 (December 10, 2014): 31111–67. http://dx.doi.org/10.5194/acpd-14-31111-2014.

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Abstract. During the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE) in the Tropics, the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) in the Arctic, and the 2010 Small PARTicles In CirrUS (SPARTICUS) campaign in mid-latitudes, high-resolution images of ice crystals were recorded by a Cloud Particle Imager at temperatures (T) between −87 and 0 °C. The projected maximum dimension (D'), length (L'), and width (W') of pristine columns, plates, and component bullets of bullet rosettes were measured using newly developed software, the Ice Crystal Ruler. The number of bullets in each bullet rosette was also measured. Column crystals were further distinguished as either horizontally oriented columns or columns with other orientations to eliminate any orientation effect on the measured dimensions. Dimensions and aspect ratios (AR, dimension of major axis divided by dimension of minor axis) of crystals were determined as functions of temperature, geophysical location, and type of cirrus. Dimensions of crystals generally increased as temperature increased. Columns and bullets had larger dimensions (i.e., W') of the minor axis (i.e., a axis) for a given dimension (i.e., D' or L') of the major axis (i.e., c axis), and thus smaller AR, as T increased, whereas this trend did not occur for plate crystals. The average number of branches in bullet rosettes was 5.50±1.35 during three campaigns and 6.32±1.34 (5.46±1.34; 4.95±1.01) during TWP-ICE (SPARTICUS; ISDAC). The AR of bullets increased with the number of branches in bullet rosettes. Most dimensions of crystals and ARs of columnar crystals measured during SPARTICUS were larger than those measured during TWP-ICE and ISDAC at −67 < T < −35 °C and at −40 < T < −15 °C, respectively. The relative occurrence of varying pristine habits depended strongly on cirrus type (i.e., anvil or non-anvil clouds), with plates especially occurring more frequently in anvils. The L–W relationships of columns derived using current data exhibited a strong dependence on temperature; similar relationship determined in previous studies were within the range of the current data.

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Um, J., G. M. McFarquhar, Y. P. Hong, S. S. Lee, C. H. Jung, R. P. Lawson, and Q. Mo. "Dimensions and aspect ratios of natural ice crystals." Atmospheric Chemistry and Physics 15, no. 7 (April 15, 2015): 3933–56. http://dx.doi.org/10.5194/acp-15-3933-2015.

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Abstract. During the 2006 Tropical Warm Pool International Cloud Experiment (TWP-ICE) in the tropics, the 2008 Indirect and Semi-Direct Aerosol Campaign (ISDAC) in the Arctic, and the 2010 Small PARTicles In CirrUS (SPARTICUS) campaign at mid-latitudes, high-resolution images of ice crystals were recorded by a Cloud Particle Imager at temperatures (T) between −87 and 0 °C. The projected maximum dimension (D'), length (L'), and width (W') of pristine columns, plates, and component bullets of bullet rosettes were measured using newly developed software, the Ice Crystal Ruler. The number of bullets in each bullet rosette was also measured. Column crystals were further distinguished as either horizontally oriented columns or columns with other orientations to eliminate any orientation effect on the measured dimensions. The dimensions and aspect ratios (AR, the dimension of the major axis divided by the dimension of the minor axis) of crystals were determined as functions of temperature, geophysical location, and type of cirrus. Dimensions of crystals generally increased with temperature. Columns and bullets had larger dimensions (i.e., W') of the minor axis (i.e., a axis) for a given dimension (i.e., D' orL') of the major axis (i.e., c axis), and thus smaller AR, as T increased, whereas this trend did not occur for plate crystals. The average number of branches in bullet rosettes was 5.50 ± 1.35 during three campaigns and 6.32 ± 1.34 (5.46 ± 1.34; 4.95 ± 1.01) during TWP-ICE (SPARTICUS; ISDAC). The AR of bullets increased with the number of branches in bullet rosettes. Most dimensions of crystals and ARs of columnar crystals measured during SPARTICUS were larger than those measured during TWP-ICE and ISDAC at −67 < T < -35 °C and at −40 < T < −15 °C, respectively. The relative occurrence of varying pristine habits depended strongly on cirrus type (i.e., anvil or non-anvil clouds), with plates especially occurring more frequently in anvils. The L–W relationships of columns derived using current data exhibited a strong dependence on temperature; similar relationships determined in previous studies were within the range of the current data.

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6

Li, Jiabo, Xindong Peng, Xiaohan Li, Yanluan Lin, and Wenchao Chu. "Evaluation of a Flexible Single Ice Microphysics and a Gaussian Probability-Density-Function Macrophysics Scheme in a Single Column Model." Atmosphere 12, no. 5 (May 17, 2021): 638. http://dx.doi.org/10.3390/atmos12050638.

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Scale-aware parameterizations of subgrid scale physics are essentials for multiscale atmospheric modeling. A single-ice (SI) microphysics scheme and Gaussian probability-density-function (Gauss-PDF) macrophysics scheme were implemented in the single-column Global-to-Regional Integrated forecast System model (SGRIST) and they were tested using the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) and the Atmospheric Radiation Measurement Southern Great Plains Experiment in 1997 (ARM97). Their performance was evaluated against observations and other reference schemes. The new schemes simulated reasonable precipitation with proper fluctuations and peaks, ice, and liquid water contents, especially in lower levels below 650 hPa during the wet period in the TWP-ICE. The root mean square error (RMSE) of the simulated cloud fraction was below 200 hPa was 0.10/0.08 in the wet/dry period, which showed an obvious improvement when compared to that, i.e., 0.11/0.11 of original scheme. Accumulated ice water content below the melting level decreased by 21.57% in the SI. The well-matched average liquid water content displayed between the new scheme and observations, which was two times larger than those with the referencing scheme. In the ARM97 simulations, the SI scheme produced considerable ice water content, especially when convection was active. Low-level cloud fraction and precipitation extremes were improved using the Gauss-PDF scheme, which displayed the RMSE of cloud fraction of 0.02, being only half of the original schemes. The study indicates that the SI and Gauss-PDF schemes are promising approaches to simplify the microphysics process and improve the low-level cloud modeling.

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7

Wapler, Kathrin, Todd P. Lane, Peter T. May, Christian Jakob, Michael J. Manton, and Steven T. Siems. "Cloud-System-Resolving Model Simulations of Tropical Cloud Systems Observed during the Tropical Warm Pool-International Cloud Experiment." Monthly Weather Review 138, no. 1 (January 1, 2010): 55–73. http://dx.doi.org/10.1175/2009mwr2993.1.

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Abstract Nested cloud-system-resolving model simulations of tropical convective clouds observed during the recent Tropical Warm Pool-International Cloud Experiment (TWP-ICE) are conducted using the Weather Research and Forecasting (WRF) model. The WRF model is configured with a highest-resolving domain that uses 1.3-km grid spacing and is centered over Darwin, Australia. The performance of the model in simulating two different convective regimes observed during TWP-ICE is considered. The first regime is characteristic of the active monsoon, which features widespread cloud cover that is similar to maritime convection. The second regime is a monsoon break, which contains intense localized systems that are representative of diurnally forced continental convection. Many aspects of the model performance are considered, including their sensitivity to physical parameterizations and initialization time, and the spatial statistics of rainfall accumulations and the rain-rate distribution. While the simulations highlight many challenges and difficulties in correctly modeling the convection in the two regimes, they show that provided the mesoscale environment is adequately reproduced by the model, the statistics of the simulated rainfall agrees reasonably well with the observations.

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8

Lin, Yanluan, L. J. Donner, J. Petch, P. Bechtold, J. Boyle, S. A. Klein, T. Komori, et al. "TWP-ICE global atmospheric model intercomparison: Convection responsiveness and resolution impact." Journal of Geophysical Research: Atmospheres 117, no. D9 (May 8, 2012): n/a. http://dx.doi.org/10.1029/2011jd017018.

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9

Balmes, Kelly, and Qiang Fu. "An Investigation of Optically Very Thin Ice Clouds from Ground-Based ARM Raman Lidars." Atmosphere 9, no. 11 (November 14, 2018): 445. http://dx.doi.org/10.3390/atmos9110445.

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Optically very thin ice clouds from the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) and ground-based Raman lidars (RL) at the atmospheric radiation measurement (ARM) sites of the Southern Great Plains (SGP) and Tropical Western Pacific (TWP) are analyzed. The optically very thin ice clouds, with ice cloud column optical depths below 0.01, are about 23% of the transparent ice-cloudy profiles from the RL, compared to 4–7% from CALIPSO. The majority (66–76%) of optically very thin ice clouds from the RLs are found to be adjacent to ice clouds with ice cloud column optical depths greater than 0.01. The temporal structure of RL-observed optically very thin ice clouds indicates a clear sky–cloud continuum. Global cloudiness estimates from CALIPSO observations leveraged with high-sensitivity RL observations suggest that CALIPSO may underestimate the global cloud fraction when considering optically very thin ice clouds.

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10

Henneberg, Olga, Jan Henneberger, and Ulrike Lohmann. "Formation and Development of Orographic Mixed-Phase Clouds." Journal of the Atmospheric Sciences 74, no. 11 (November 1, 2017): 3703–24. http://dx.doi.org/10.1175/jas-d-16-0348.1.

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Abstract Orographic forcing can stabilize mixed-phase clouds (MPCs), which are thermodynamically unstable owing to the different saturation vapor pressure over liquid water and ice. This study presents simulations of MPCs in orographically complex terrain over the Alpine ridge with the regional model COSMO using a horizontal resolution of 1 km. Two case studies provide insights into the formation of Alpine MPCs. Trajectory studies show that the majority of the air parcels lifted by more than 600 m are predominantly in the liquid phase even if they originate from glaciated clouds. The interplay between lifted and advected air parcels is crucial for the occurrence of MPCs. Within a sensitivity study, the orography is reduced to 80%, which changed both the total barrier height and steepness. The changes in total water path (TWP), liquid water path (LWP), and ice water path (IWP) vary in sign and strength as the affected precipitation does. LWP can experience changes up to 500% resulting in a transformation from an ice-dominated MPC to a liquid-dominated MPC. In further simulations with increased steepness and maintained surface height at Jungfraujoch, TWP experiences a reduction between 25% and 40% during different time periods, which results in reduced precipitation by around 30%. An accurate representation of the steepness and the height of mountains in models is crucial for the formation and development of MPCs.

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11

Protat, A., G. M. McFarquhar, J. Um, and J. Delanoë. "Obtaining Best Estimates for the Microphysical and Radiative Properties of Tropical Ice Clouds from TWP-ICE In Situ Microphysical Observations." Journal of Applied Meteorology and Climatology 50, no. 4 (April 2011): 895–915. http://dx.doi.org/10.1175/2010jamc2401.1.

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AbstractBest estimates of the bulk microphysical and radiative properties (ice water content, visible extinction, effective radius, and total concentration) are derived for three case studies of tropical ice clouds sampled during the Tropical Warm Pool International Cloud Experiment (TWP-ICE). Two case studies are aged cirrus clouds produced by deep convection (the so-called 27/01 and 29/01 cases), and the third (“02/02”) is a fresh anvil produced by deep convective activity over the Tiwi Islands. Using crystal images obtained by a Cloud Particle Imager (CPI), it is observed that small ice particles (with maximum dimension D < 50–100 μm) were predominantly quasi spherical, with the degree of nonsphericity increasing rapidly in the 50 < D < 100-μm range. For D > 100 μm, the aged cirrus clouds were predominantly characterized by bullet rosettes and aggregates of bullet rosettes, plates, and columns. In contrast, the fresh anvil had more frequent occurrences of plates, columns, aggregates of plates, and occasionally capped columns. The impact of shattering of large ice crystals on probe tips and the overall quality of the TWP-ICE in situ microphysical measurements are assessed. It is suggested that shattering has a relatively small impact on the CPI and cloud droplet probe (CDP) TWP-ICE data and a large impact on the Cloud Aerosol Spectrometer data, as already documented by others. It is also shown that the CPI size distributions must be multiplied by a factor of 4 to match those of the cloud imaging probe (CIP) for maximum dimension larger than 100 μm (taken as a reference). A technique [named Best Estimate of Area and Density (BEAD)] to minimize errors associated with the density (ρ)–D and projected area (A)–D assumptions in bulk microphysics calculation is introduced and applied to the TWP-ICE data. The method makes direct use of the frequency of occurrence of each particle habit as classified from the CPI data and prescribed ρ–D and A–D relationships from the literature. This approach produces ice water content (IWC) estimates that are virtually unbiased relative to bulk measures obtained from a counterflow spectrometer and impactor (CSI) probe. In contrast, the use of ρ–D and A–D relationships for single habits does produce large biases relative to the CSI observations: from −50% for bullet rosettes to +70%–80% for aggregates. The so-called width, length, area, and perimeter (WLAP) technique, which also makes use of individual CPI images, is found to produce positively biased IWCs (by 40% or so), and has a standard deviation of the errors similar to the BEAD technique. The impact of the large variability of the size distributions measured by different probe combinations on the bulk microphysical properties is characterized. The mean fractional differences with respect to the CSI measurements are small for the CPI + CIP, CPI, and CDP + CIP combinations (2.2%, −0.8%, and −1.1%, respectively), with standard deviations of the fractional differences ranging from 7% to 9%. This result provides an independent validation of the CPI scaling factor. The fractional differences produced between the CPI + CIP, CPI, and CDP + CIP combinations for extinction, effective radius, and total concentration are 33%, 10%–20%, and 90%, respectively, with relatively small standard deviations of 5%–8%. The fractional difference on total concentration varies greatly over the concentration range though, with values being larger than a factor of 2 for total concentrations smaller than 40 L−1, but reducing to 10%–20% for concentrations larger than 100 L−1. Therefore, caution should be exercised when using total concentrations smaller than 60–80 L−1 as references for radar–lidar retrieval evaluation.

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Del Genio, Anthony D., Jingbo Wu, and Yonghua Chen. "Characteristics of Mesoscale Organization in WRF Simulations of Convection during TWP-ICE." Journal of Climate 25, no. 17 (May 24, 2012): 5666–88. http://dx.doi.org/10.1175/jcli-d-11-00422.1.

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Abstract Compared to satellite-derived heating profiles, the Goddard Institute for Space Studies general circulation model (GCM) convective heating is too deep and its stratiform upper-level heating is too weak. This deficiency highlights the need for GCMs to parameterize the mesoscale organization of convection. Cloud-resolving model simulations of convection near Darwin, Australia, in weak wind shear environments of different humidities are used to characterize mesoscale organization processes and to provide parameterization guidance. Downdraft cold pools appear to stimulate further deep convection both through their effect on eddy size and vertical velocity. Anomalously humid air surrounds updrafts, reducing the efficacy of entrainment. Recovery of cold pool properties to ambient conditions over 5–6 h proceeds differently over land and ocean. Over ocean increased surface fluxes restore the cold pool to prestorm conditions. Over land surface fluxes are suppressed in the cold pool region; temperature decreases and humidity increases, and both then remain nearly constant, while the undisturbed environment cools diurnally. The upper-troposphere stratiform rain region area lags convection by 5–6 h under humid active monsoon conditions but by only 1–2 h during drier break periods, suggesting that mesoscale organization is more readily sustained in a humid environment. Stratiform region hydrometeor mixing ratio lags convection by 0–2 h, suggesting that it is strongly influenced by detrainment from convective updrafts. Small stratiform region temperature anomalies suggest that a mesoscale updraft parameterization initialized with properties of buoyant detrained air and evolving to a balance between diabatic heating and adiabatic cooling might be a plausible approach for GCMs.

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Fridlind, A. M., A. S. Ackerman, J. P. Chaboureau, J. Fan, W. W. Grabowski, A. A. Hill, T. R. Jones, et al. "A comparison of TWP-ICE observational data with cloud-resolving model results." Journal of Geophysical Research: Atmospheres 117, no. D5 (March 13, 2012): n/a. http://dx.doi.org/10.1029/2011jd016595.

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Davies, L., C. Jakob, K. Cheung, A. Del Genio, A. Hill, T. Hume, R. J. Keane, et al. "A single-column model ensemble approach applied to the TWP-ICE experiment." Journal of Geophysical Research: Atmospheres 118, no. 12 (June 24, 2013): 6544–63. http://dx.doi.org/10.1002/jgrd.50450.

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15

Hankinson, Mai C. N., M. J. Reeder, and T. P. Lane. "Gravity waves generated by convection during TWP-ICE: I. Inertia-gravity waves." Journal of Geophysical Research: Atmospheres 119, no. 9 (May 13, 2014): 5269–82. http://dx.doi.org/10.1002/2013jd020724.

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Petch, Jon, Adrian Hill, Laura Davies, Ann Fridlind, Christian Jakob, Yanluan Lin, Shaoecheng Xie, and Ping Zhu. "Evaluation of intercomparisons of four different types of model simulating TWP-ICE." Quarterly Journal of the Royal Meteorological Society 140, no. 680 (July 18, 2013): 826–37. http://dx.doi.org/10.1002/qj.2192.

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Matrosov, S. Y. "Synergetic use of millimeter and centimeter wavelength radars for retrievals of cloud and rainfall parameters." Atmospheric Chemistry and Physics Discussions 10, no. 1 (January 18, 2010): 947–75. http://dx.doi.org/10.5194/acpd-10-947-2010.

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Abstract. A remote sensing approach for simultaneous retrievals of cloud and rainfall parameters in the vertical column above the US Department of Energy's (DOE) Climate Research Facility at the Tropical Western Pacific (TWP) Darwin site in Australia is described. This approach uses vertically pointing measurements from a DOE Ka-band radar and scanning measurements from a nearby C-band radar pointing toward the TWP Darwin site. Rainfall retrieval constraints are provided by data from a surface impact disdrometer. The approach is applicable to stratiform precipitating cloud systems when a separation between the liquid hydrometeor layer, which contains rainfall and liquid water clouds, and the ice hydrometeor layer is provided by the radar bright band. Absolute C-band reflectivities and Ka-band vertical reflectivity gradients in the liquid layer are used for retrievals of the mean layer rain rate and cloud liquid water path (CLWP). C-band radar reflectivities are also used to estimate ice water path (IWP) in regions above the melting layer. The retrieval uncertainties of CLWP and IWP for typical stratiform precipitation systems are about 500–800 g m−2 (for CLWP) and a factor of 2 (for IWP). The CLWP retrieval uncertainties increase with rain rate, so retrievals for higher rain rates may be impractical. The expected uncertainties of layer mean rain rate retrievals are around 20%, which, in part, is due to constraints available from the disdrometer data. The applicability of the suggested approach is illustrated for two characteristic events observed at the TWP Darwin site during the wet season of 2007. A future deployment of W-band radars at the DOE tropical Climate Research Facilities can improve CLWP estimate accuracies and provide retrievals for a wider range of stratiform precipitating cloud events.

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Matrosov, S. Y. "Synergetic use of millimeter- and centimeter-wavelength radars for retrievals of cloud and rainfall parameters." Atmospheric Chemistry and Physics 10, no. 7 (April 7, 2010): 3321–31. http://dx.doi.org/10.5194/acp-10-3321-2010.

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Abstract. A remote sensing approach for simultaneous retrievals of cloud and rainfall parameters in the vertical column above the US Department of Energy's (DOE) Climate Research Facility at the Tropical Western Pacific (TWP) Darwin site in Australia is described. This approach uses vertically pointing measurements from a DOE Ka-band radar and scanning measurements from a nearby C-band radar pointing toward the TWP Darwin site. Rainfall retrieval constraints are provided by data from a surface impact disdrometer. The approach is applicable to stratiform precipitating cloud systems when a separation between the liquid hydrometeor layer, which contains rainfall and liquid water clouds, and the ice hydrometeor layer is provided by the radar bright band. Absolute C-band reflectivities and Ka-band vertical reflectivity gradients in the liquid layer are used for retrievals of the mean layer rain rate and cloud liquid water path (CLWP). C-band radar reflectivities are also used to estimate ice water path (IWP) in regions above the melting layer. The retrieval uncertainties of CLWP and IWP for typical stratiform precipitation systems are about 500–800 g m−2 (for CLWP) and a factor of 2 (for IWP). The CLWP retrieval uncertainties increase with rain rate, so retrievals for higher rain rates may be impractical. The expected uncertainties of layer mean rain rate retrievals are around 20%, which, in part, is due to constraints available from the disdrometer data. The applicability of the suggested approach is illustrated for two characteristic events observed at the TWP Darwin site during the wet season of 2007. A future deployment of W-band radars at the DOE tropical Climate Research Facilities can improve CLWP estimation accuracies and provide retrievals for a wider range of stratiform precipitating cloud events.

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Leung, Kimberly, Max Velado, Aneesh Subramanian, Guang J. Zhang, Richard C. J. Somerville, and Samuel S. P. Shen. "Simulation of High-Resolution Precipitable Water Data by a Stochastic Model with a Random Trigger." Advances in Data Science and Adaptive Analysis 08, no. 02 (April 2016): 1650006. http://dx.doi.org/10.1142/s2424922x16500066.

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We use a stochastic differential equation (SDE) model with a random precipitation trigger for mass balance to simulate the 20 s temporal resolution column precipitable water vapor (PWV) data during the tropical warm pool international cloud experiment (TWP-ICE) period of January 20 to February 15, 2006 at Darwin, Australia. The trigger is determined by an exponential cumulative distribution function, the time step size in the SDE simulation, and a random precipitation indicator uniformly distributed over [0, 1]. Compared with the observed data, the simulations have similar means, extremes, skewness, kurtosis, and overall shapes of probability distribution, and are temporally well synchronized for increasing and decreasing, but have about 20% lower standard deviation. Based on a 1000-day run, the correlations between the model data and the observations in TWP-ICE period were computed in a moving time window of 25 days and show quasi-periodic variations between (−0.675, 0.697). This shows that the results are robust for the stochastic model simulation of the observed PWV data, whose fractal dimension is 1.9, while the dimension of the simulated data is also about 1.9. This agreement and numerous sensitivity experiments form a test on the feasibility of using an SDE model to simulate precipitation processes in more complex climate models.

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Van Weverberg, K., A. M. Vogelmann, W. Lin, E. P. Luke, A. Cialella, P. Minnis, M. Khaiyer, E. R. Boer, and M. P. Jensen. "The Role of Cloud Microphysics Parameterization in the Simulation of Mesoscale Convective System Clouds and Precipitation in the Tropical Western Pacific." Journal of the Atmospheric Sciences 70, no. 4 (April 1, 2013): 1104–28. http://dx.doi.org/10.1175/jas-d-12-0104.1.

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Abstract This paper presents a detailed analysis of convection-permitting cloud simulations, aimed at increasing the understanding of the role of parameterized cloud microphysics in the simulation of mesoscale convective systems (MCSs) in the tropical western Pacific (TWP). Simulations with three commonly used bulk microphysics parameterizations with varying complexity have been compared against satellite-retrieved cloud properties. An MCS identification and tracking algorithm was applied to the observations and the simulations to evaluate the number, spatial extent, and microphysical properties of individual cloud systems. Different from many previous studies, these individual cloud systems could be tracked over larger distances because of the large TWP domain studied. The analysis demonstrates that the simulation of MCSs is very sensitive to the parameterization of microphysical processes. The most crucial element was found to be the fall velocity of frozen condensate. Differences in this fall velocity between the experiments were more related to differences in particle number concentrations than to fall speed parameterization. Microphysics schemes that exhibit slow sedimentation rates for ice aloft experience a larger buildup of condensate in the upper troposphere. This leads to more numerous and/or larger MCSs with larger anvils. Mean surface precipitation was found to be overestimated and insensitive to the microphysical schemes employed in this study. In terms of the investigated properties, the performances of complex two-moment schemes were not superior to the simpler one-moment schemes, since explicit prediction of number concentration does not necessarily improve processes such as ice nucleation, the aggregation of ice crystals into snowflakes, and their sedimentation characteristics.

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Collis, Scott, Alain Protat, Peter T. May, and Christopher Williams. "Statistics of Storm Updraft Velocities from TWP-ICE Including Verification with Profiling Measurements." Journal of Applied Meteorology and Climatology 52, no. 8 (August 2013): 1909–22. http://dx.doi.org/10.1175/jamc-d-12-0230.1.

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AbstractComparisons between direct measurements and modeled values of vertical air motions in precipitating systems are complicated by differences in temporal and spatial scales. On one hand, vertically profiling radars more directly measure the vertical air motion but do not adequately capture full storm dynamics. On the other hand, vertical air motions retrieved from two or more scanning Doppler radars capture the full storm dynamics but require model constraints that may not capture all updraft features because of inadequate sampling, resolution, numerical constraints, and the fact that the storm is evolving as it is scanned by the radars. To investigate the veracity of radar-based retrievals, which can be used to verify numerically modeled vertical air motions, this article presents several case studies from storm events around Darwin, Northern Territory, Australia, in which measurements from a dual-frequency radar profiler system and volumetric radar-based wind retrievals are compared. While a direct comparison was not possible because of instrumentation location, an indirect comparison shows promising results, with volume retrievals comparing well to those obtained from the profiling system. This prompted a statistical analysis of an extended period of an active monsoon period during the Tropical Warm Pool International Cloud Experiment (TWP-ICE). Results show less vigorous deep convective cores with maximum updraft velocities occurring at lower heights than some cloud-resolving modeling studies suggest.

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Xie, Shaocheng, Timothy Hume, Christian Jakob, Stephen A. Klein, Renata B. McCoy, and Minghua Zhang. "Observed Large-Scale Structures and Diabatic Heating and Drying Profiles during TWP-ICE." Journal of Climate 23, no. 1 (January 1, 2010): 57–79. http://dx.doi.org/10.1175/2009jcli3071.1.

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Abstract This study documents the characteristics of the large-scale structures and diabatic heating and drying profiles observed during the Tropical Warm Pool–International Cloud Experiment (TWP-ICE), which was conducted in January–February 2006 in Darwin during the northern Australian monsoon season. The examined profiles exhibit significant variations between four distinct synoptic regimes that were observed during the experiment. The active monsoon period is characterized by strong upward motion and large advective cooling and moistening throughout the entire troposphere, while the suppressed and clear periods are dominated by moderate midlevel subsidence and significant low- to midlevel drying through horizontal advection. The midlevel subsidence and horizontal dry advection are largely responsible for the dry midtroposphere observed during the suppressed period and limit the growth of clouds to low levels. During the break period, upward motion and advective cooling and moistening located primarily at midlevels dominate together with weak advective warming and drying (mainly from horizontal advection) at low levels. The variations of the diabatic heating and drying profiles with the different regimes are closely associated with differences in the large-scale structures, cloud types, and rainfall rates between the regimes. Strong diabatic heating and drying are seen throughout the troposphere during the active monsoon period while they are moderate and only occur above 700 hPa during the break period. The diabatic heating and drying tend to have their maxima at low levels during the suppressed periods. The diurnal variations of these structures between monsoon systems, continental/coastal, and tropical inland-initiated convective systems are also examined.

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Hankinson, Mai C. N., M. J. Reeder, and T. P. Lane. "Gravity waves generated by convection during TWP-ICE: 2. High-frequency gravity waves." Journal of Geophysical Research: Atmospheres 119, no. 9 (May 13, 2014): 5257–68. http://dx.doi.org/10.1002/2013jd020726.

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Tao, QING, SHEN Xin-Yong, WANG Wei-Guo, and HUANG Wen-Yan. "Characteristics of Lagrangian Transportation in a Tropical Deep Convective Process During TWP-ICE." Chinese Journal of Geophysics 57, no. 5 (September 2014): 698–711. http://dx.doi.org/10.1002/cjg2.20134.

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25

Zhang, Guang J., Xiaoqing Wu, Xiping Zeng, and Toni Mitovski. "Estimation of convective entrainment properties from a cloud-resolving model simulation during TWP-ICE." Climate Dynamics 47, no. 7-8 (December 30, 2015): 2177–92. http://dx.doi.org/10.1007/s00382-015-2957-7.

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26

McFarquhar, Greg M., Junshik Um, Matt Freer, Darrel Baumgardner, Gregory L. Kok, and Gerald Mace. "Importance of small ice crystals to cirrus properties: Observations from the Tropical Warm Pool International Cloud Experiment (TWP-ICE)." Geophysical Research Letters 34, no. 13 (July 14, 2007): n/a. http://dx.doi.org/10.1029/2007gl029865.

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27

Morales Betancourt, R., D. Lee, L. Oreopoulos, Y. C. Sud, D. Barahona, and A. Nenes. "Sensitivity of cirrus and mixed-phase clouds to the ice nuclei spectra in McRAS-AC: single column model simulations." Atmospheric Chemistry and Physics 12, no. 22 (November 16, 2012): 10679–92. http://dx.doi.org/10.5194/acp-12-10679-2012.

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Abstract. The salient features of mixed-phase and ice clouds in a GCM cloud scheme are examined using the ice nucleation parameterizations of Liu and Penner (LP) and Barahona and Nenes (BN). The performance of both parameterizations was assessed in the GEOS-5 AGCM using the McRAS-AC cloud microphysics framework in single column mode. Four dimensional assimilated data from the intensive observation period of ARM TWP-ICE campaign was used to drive the fluxes and lateral forcing. Simulation experiments were established to test the impact of each parameterization in the resulting cloud fields. Three commonly used IN spectra were utilized in the BN parameterization to describe the availability of IN for heterogeneous ice nucleation. The results showed large similarities in the cirrus cloud regime between all the schemes tested, in which ice crystal concentrations were within a factor of 10 regardless of the parameterization used. In mixed-phase clouds there were some persistent differences in cloud particle number concentration and size, as well as in cloud fraction, ice water mixing ratio, and ice water path. Contact freezing in the simulated mixed-phase clouds contributed to the effective transfer of liquid to ice, so that on average, the clouds were fully glaciated at T 260 K, irrespective of the ice nucleation parameterization used. Comparison of simulated ice water path to available satellite derived observations were also performed, finding that all the schemes tested with the BN parameterization predicted average values of IWP within ±15% of the observations.

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28

Morales Betancourt, R., D. Lee, L. Oreopoulos, Y. C. Sud, D. Barahona, and A. Nenes. "Sensitivity of cirrus and mixed-phase clouds to the ice nuclei spectra in McRAS-AC: single column model simulations." Atmospheric Chemistry and Physics Discussions 12, no. 6 (June 12, 2012): 14927–57. http://dx.doi.org/10.5194/acpd-12-14927-2012.

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Abstract. The salient features of mixed-phase and ice clouds in a GCM cloud scheme are examined using the ice formation parameterizations of Liu and Penner (LP) and Barahona and Nenes (BN). The performance of LP and BN ice nucleation parameterizations were assessed in the GEOS-5 AGCM using the McRAS-AC cloud microphysics framework in single column mode. Four dimensional assimilated data from the intensive observation period of ARM TWP-ICE campaign was used to drive the fluxes and lateral forcing. Simulation experiments where established to test the impact of each parameterization in the resulting cloud fields. Three commonly used IN spectra were utilized in the BN parameterization to described the availability of IN for heterogeneous ice nucleation. The results show large similarities in the cirrus cloud regime between all the schemes tested, in which ice crystal concentrations were within a factor of 10 regardless of the parameterization used. In mixed-phase clouds there are some persistent differences in cloud particle number concentration and size, as well as in cloud fraction, ice water mixing ratio, and ice water path. Contact freezing in the simulated mixed-phase clouds contributed to transfer liquid to ice efficiently, so that on average, the clouds were fully glaciated at T~260 K, irrespective of the ice nucleation parameterization used. Comparison of simulated ice water path to available satellite derived observations were also performed, finding that all the schemes tested with the BN parameterization predicted average values of IWP within ±15% of the observations.

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29

Zhu, Ping, Jim Dudhia, Paul R. Field, Kathrin Wapler, Ann Fridlind, Adam Varble, Ed Zipser, Jon Petch, Ming Chen, and Zhenduo Zhu. "A limited area model (LAM) intercomparison study of a TWP-ICE active monsoon mesoscale convective event." Journal of Geophysical Research: Atmospheres 117, no. D11 (June 6, 2012): n/a. http://dx.doi.org/10.1029/2011jd016447.

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Evan, Stephanie, M. Joan Alexander, and Jimy Dudhia. "Model Study of Intermediate-Scale Tropical Inertia–Gravity Waves and Comparison to TWP-ICE Campaign Observations." Journal of the Atmospheric Sciences 69, no. 2 (February 1, 2012): 591–610. http://dx.doi.org/10.1175/jas-d-11-051.1.

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Abstract A 2-day inertia–gravity wave (IGW) was observed in high-resolution radiosonde soundings of horizontal wind and temperature taken during the 2006 Tropical Warm Pool–International Cloud Experiment (TWP-ICE) experiment in the Darwin area. The wave was observed in the stratosphere above Darwin from 28 January to 5 February. A similar wave event is observed in the European Centre for Medium-Range Weather Forecasts (ECMWF) operational data. A comparison between the characteristics of the IGW derived with the ECMWF data to the properties of the wave derived with the radiosonde data shows that the ECMWF data capture similar structure for this 2-day wave event but with a larger vertical wavelength. A reverse ray-tracing method is used to localize the source region. Using ECMWF data to define the atmospheric background conditions and wave properties observed in the soundings, it is found that the 2-day wave event originated from deep convection in the Indonesian region around 20 January. The Weather Research and Forecasting (WRF) modeling system is used to complement the ECMWF data to assess the influence of vertical resolution and initial conditions on the wave structure. The model domain is configured as a tropical channel and the ECMWF analyses provide the north/south boundaries and initial conditions. WRF is used with the same horizontal resolution (40 km) as the operational ECMWF in 2006 while using a finer vertical grid spacing than ECMWF. The model is run from 18 January to 11 February to cover the wave life cycle. Different experiments are also performed to determine the sensitivity of the wave structure to cumulus schemes, initial conditions, and vertical resolution. The 2-day wave properties resulting from the WRF experiments are compared to those retrieved from the radiosonde data and from the ECMWF analyses. It is demonstrated that higher vertical resolution would be required for ECMWF to accurately resolve the vertical structure of the wave and its effect on the middle-atmospheric circulation.

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31

Kim, So-Young, Ji-Young Han, In-Jin Choi, and Soo Ya Bae. "Evaluation of cloud and precipitation parameterization using a single-column model: A TWP-ICE case study." Asia-Pacific Journal of Atmospheric Sciences 50, no. 4 (June 6, 2014): 469–80. http://dx.doi.org/10.1007/s13143-014-0037-2.

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32

Deutscher, N. M., D. W. T. Griffith, G. W. Bryant, P. O. Wennberg, G. C. Toon, R. A. Washenfelder, G. Keppel-Aleks, et al. "Total column CO<sub>2</sub> measurements at Darwin, Australia – site description and calibration against in situ aircraft profiles." Atmospheric Measurement Techniques Discussions 3, no. 2 (March 17, 2010): 989–1021. http://dx.doi.org/10.5194/amtd-3-989-2010.

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Abstract. An automated Fourier Transform Spectroscopic (FTS) solar observatory was established in Darwin, Australia in August 2005. The laboratory is part of the Total Carbon Column Observing Network, and measures atmospheric column abundances of CO2 and O2 and other gases. Measured CO2 columns were calibrated against integrated aircraft profiles obtained during the TWP-ICE campaign in January–February 2006, and show good agreement with calibrations for a similar instrument in Park Falls, Wisconsin. A clear-sky low airmass relative precision of 0.1% is demonstrated in the CO2 and O2 retrieved column-averaged volume mixing ratios. The 1% negative bias in the FTS XCO2 relative to the World Meteorological Organization (WMO) calibrated in situ scale is within the uncertainties of the NIR spectroscopy and analysis.

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33

Deutscher, N. M., D. W. T. Griffith, G. W. Bryant, P. O. Wennberg, G. C. Toon, R. A. Washenfelder, G. Keppel-Aleks, et al. "Total column CO<sub>2</sub> measurements at Darwin, Australia – site description and calibration against in situ aircraft profiles." Atmospheric Measurement Techniques 3, no. 4 (July 19, 2010): 947–58. http://dx.doi.org/10.5194/amt-3-947-2010.

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Abstract. An automated Fourier Transform Spectroscopic (FTS) solar observatory was established in Darwin, Australia in August 2005. The laboratory is part of the Total Carbon Column Observing Network, and measures atmospheric column abundances of CO2 and O2 and other gases. Measured CO2 columns were calibrated against integrated aircraft profiles obtained during the TWP-ICE campaign in January–February 2006, and show good agreement with calibrations for a similar instrument in Park Falls, Wisconsin. A clear-sky low airmass relative precision of 0.1% is demonstrated in the CO2 and O2 retrieved column-averaged volume mixing ratios. The 1% negative bias in the FTS XCO2 relative to the World Meteorological Organization (WMO) calibrated in situ scale is within the uncertainties of the NIR spectroscopy and analysis.

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34

Varble, Adam, Ann M. Fridlind, Edward J. Zipser, Andrew S. Ackerman, Jean-Pierre Chaboureau, Jiwen Fan, Adrian Hill, Sally A. McFarlane, Jean-Pierre Pinty, and Ben Shipway. "Correction to “Evaluation of cloud-resolving model intercomparison simulations using TWP-ICE observations: Precipitation and cloud structure”." Journal of Geophysical Research: Atmospheres 117, no. D16 (August 25, 2012): n/a. http://dx.doi.org/10.1029/2012jd017963.

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35

Li, Zhe, Qijun Liu, Zhanshan Ma, Jiong Chen, and Qingu Jiang. "Simulation Study of Cloud Properties Affected by Heterogeneous Nucleation Using the GRAPES_SCM during the TWP-ICE Campaign." Journal of Meteorological Research 33, no. 4 (August 2019): 734–46. http://dx.doi.org/10.1007/s13351-019-8203-1.

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36

Varble, Adam, Edward J. Zipser, Ann M. Fridlind, Ping Zhu, Andrew S. Ackerman, Jean-Pierre Chaboureau, Jiwen Fan, Adrian Hill, Ben Shipway, and Christopher Williams. "Evaluation of cloud-resolving and limited area model intercomparison simulations using TWP-ICE observations: 2. Precipitation microphysics." Journal of Geophysical Research: Atmospheres 119, no. 24 (December 18, 2014): 13,919–13,945. http://dx.doi.org/10.1002/2013jd021372.

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37

Yue, Qing, K. N. Liou, S. C. Ou, B. H. Kahn, P. Yang, and G. G. Mace. "Interpretation of AIRS Data in Thin Cirrus Atmospheres Based on a Fast Radiative Transfer Model." Journal of the Atmospheric Sciences 64, no. 11 (November 1, 2007): 3827–42. http://dx.doi.org/10.1175/2007jas2043.1.

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Abstract A thin cirrus cloud thermal infrared radiative transfer model has been developed for application to cloudy satellite data assimilation. This radiation model was constructed by combining the Optical Path Transmittance (OPTRAN) model, developed for the speedy calculation of transmittances in clear atmospheres, and a thin cirrus cloud parameterization using a number of observed ice crystal size and shape distributions. Numerical simulations show that cirrus cloudy radiances in the 800–1130-cm−1 thermal infrared window are sufficiently sensitive to variations in cirrus optical depth and ice crystal size as well as in ice crystal shape if appropriate habit distribution models are selected a priori for analysis. The parameterization model has been applied to the Atmospheric Infrared Sounder (AIRS) on board the Aqua satellite to interpret clear and thin cirrus spectra observed in the thermal infrared window. Five clear and 29 thin cirrus cases at nighttime over and near the Atmospheric Radiation Measurement program (ARM) tropical western Pacific (TWP) Manus Island and Nauru Island sites have been chosen for this study. A χ2-minimization program was employed to infer the cirrus optical depth and ice crystal size and shape from the observed AIRS spectra. Independent validation shows that the AIRS-inferred cloud parameters are consistent with those determined from collocated ground-based millimeter-wave cloud radar measurements. The coupled thin cirrus radiative transfer parameterization and OPTRAN, if combined with a reliable thin cirrus detection scheme, can be effectively used to enhance the AIRS data volume for data assimilation in numerical weather prediction models.

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38

Yeh, Hsi-Chyi, and Xiouhua Fu. "Incorporating Additional Sounding Observations in Weather Analysis and Rainfall Prediction During the Intensive Observing Period of 2006 TWP-ICE." Terrestrial, Atmospheric and Oceanic Sciences 22, no. 4 (2011): 421. http://dx.doi.org/10.3319/tao.2011.04.11.01(a).

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39

Prat, Olivier P., Ana P. Barros, and Christopher R. Williams. "An Intercomparison of Model Simulations and VPR Estimates of the Vertical Structure of Warm Stratiform Rainfall during TWP-ICE." Journal of Applied Meteorology and Climatology 47, no. 11 (November 1, 2008): 2797–815. http://dx.doi.org/10.1175/2008jamc1801.1.

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Abstract A model of rain shaft microphysics that solves the stochastic advection–coalescence–breakup equation in an atmospheric column was used to simulate the evolution of a stratiform rainfall event during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) in Darwin, Australia. For the first time, a dynamic simulation of the evolution of the drop spectra within a one-dimensional rain shaft is performed using realistic boundary conditions retrieved from real rain events. Droplet size distribution (DSD) retrieved from vertically pointing radar (VPR) measurements are sequentially imposed at the top of the rain shaft as boundary conditions to emulate a realistic rain event. Time series of model profiles of integral parameters such as reflectivity, rain rate, and liquid water content were subsequently compared with estimates retrieved from vertically pointing radars and Joss–Waldvogel disdrometer (JWD) observations. Results obtained are within the VPR retrieval uncertainty estimates. Besides evaluating the model’s ability to capture the dynamical evolution of the DSD within the rain shaft, a case study was conducted to assess the potential use of the model as a physically based interpolator to improve radar retrieval at low levels in the atmosphere. Numerical results showed that relative improvements on the order of 90% in the estimation of rain rate and liquid water content can be achieved close to the ground where the VPR estimates are less reliable. These findings raise important questions with regard to the importance of bin resolution and the lack of sensitivity for small raindrop size (<0.03 cm) in the interpretation of JWD data, and the implications of using disdrometer data to calibrate radar algorithms.

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40

Franklin, Charmaine N., Christian Jakob, Martin Dix, Alain Protat, and Greg Roff. "Assessing the performance of a prognostic and a diagnostic cloud scheme using single column model simulations of TWP-ICE." Quarterly Journal of the Royal Meteorological Society 138, no. 664 (November 7, 2011): 734–54. http://dx.doi.org/10.1002/qj.954.

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41

Varble, Adam, Edward J. Zipser, Ann M. Fridlind, Ping Zhu, Andrew S. Ackerman, Jean-Pierre Chaboureau, Scott Collis, Jiwen Fan, Adrian Hill, and Ben Shipway. "Evaluation of cloud-resolving and limited area model intercomparison simulations using TWP-ICE observations: 1. Deep convective updraft properties." Journal of Geophysical Research: Atmospheres 119, no. 24 (December 18, 2014): 13,891–13,918. http://dx.doi.org/10.1002/2013jd021371.

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42

Morrison, H., and W. W. Grabowski. "Cloud-system resolving model simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment." Atmospheric Chemistry and Physics Discussions 11, no. 5 (May 23, 2011): 15573–629. http://dx.doi.org/10.5194/acpd-11-15573-2011.

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Abstract. This paper presents results from 240-member ensemble simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment. Simulations using a two-dimensional cloud system-resolving model are run with pristine, polluted, or highly polluted aerosol conditions and large-scale forcing from a 6-day period of active monsoon conditions during the 2006 Tropical Warm Pool – International Cloud Experiment (TWP-ICE). Domain-mean surface precipitation is insensitive to aerosols primarily because the large-scale forcing is prescribed and dominates the water and static energy budgets. The spread of the top-of-atmosphere (TOA) shortwave and longwave radiative fluxes among different ensemble members for the same aerosol loading is surprisingly large, exceeding 25 W m−2 even when averaged over the 6-day period. This variability is caused by random fluctuations in the strength and timing of individual deep convective events. The ensemble approach demonstrates a small weakening of convection averaged over the 6-day period in the polluted simulations compared to pristine. Despite this weakening, the cloud top heights and anvil ice mixing ratios are higher in polluted conditions. This occurs because of the larger concentrations of cloud droplets that freeze, leading directly to higher ice particle concentrations, smaller ice particle sizes, and smaller fall velocities compared to simulations with pristine aerosols. Weaker convection in polluted conditions is a direct result of the changes in anvil ice characteristics and subsequent upper-tropospheric radiative heating and weaker tropospheric destabilization. Such a conclusion offers a different interpretation of recent satellite observations of tropical deep convection in pristine and polluted environments compared to the hypothesis of aerosol-induced convective invigoration. Sensitivity tests using the ensemble approach with modified microphysical parameters or domain configuration (horizontal gridlength, domain size) produce results that are similar to baseline, although there are quantitative differences in estimates of aerosol impacts on TOA radiative fluxes.

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43

Morrison, H., and W. W. Grabowski. "Cloud-system resolving model simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment." Atmospheric Chemistry and Physics 11, no. 20 (October 24, 2011): 10503–23. http://dx.doi.org/10.5194/acp-11-10503-2011.

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Abstract. This paper presents results from 240-member ensemble simulations of aerosol indirect effects on tropical deep convection and its thermodynamic environment. Simulations using a two-dimensional cloud-system resolving model are run with pristine, polluted, or highly polluted aerosol conditions and large-scale forcing from a 6-day period of active monsoon conditions during the 2006 Tropical Warm Pool – International Cloud Experiment (TWP-ICE). Domain-mean surface precipitation is insensitive to aerosols primarily because the large-scale forcing is prescribed and dominates the water and static energy budgets. The spread of the top-of-atmosphere (TOA) shortwave and longwave radiative fluxes among different ensemble members for the same aerosol loading is surprisingly large, exceeding 25 W m−2 even when averaged over the 6-day period. This variability is caused by random fluctuations in the strength and timing of individual deep convective events. The ensemble approach demonstrates a small weakening of convection averaged over the 6-day period in the polluted simulations compared to pristine. Despite this weakening, the cloud top heights and anvil ice mixing ratios are higher in polluted conditions. This occurs because of the larger concentrations of cloud droplets that freeze, leading directly to higher ice particle concentrations, smaller ice particle sizes, and smaller fall velocities compared to simulations with pristine aerosols. Weaker convection in polluted conditions is a direct result of the changes in anvil ice characteristics and subsequent upper-tropospheric radiative heating and weaker tropospheric destabilization. Such a conclusion offers a different interpretation of recent satellite observations of tropical deep convection in pristine and polluted environments compared to the hypothesis of aerosol-induced convective invigoration. Sensitivity tests using the ensemble approach with modified microphysical parameters or domain configuration (horizontal gridlength, domain size) produce results that are similar to baseline, although there are quantitative differences in estimates of aerosol impacts on TOA radiative fluxes.

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44

Balmes, K. A., Q. Fu, and T. J. Thorsen. "Differences in Ice Cloud Optical Depth From CALIPSO and Ground-Based Raman Lidar at the ARM SGP and TWP Sites." Journal of Geophysical Research: Atmospheres 124, no. 3 (February 12, 2019): 1755–78. http://dx.doi.org/10.1029/2018jd028321.

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45

Wang, Hailong, Casey D. Burleyson, Po-Lun Ma, Jerome D. Fast, and Philip J. Rasch. "Using the Atmospheric Radiation Measurement (ARM) Datasets to Evaluate Climate Models in Simulating Diurnal and Seasonal Variations of Tropical Clouds." Journal of Climate 31, no. 8 (March 27, 2018): 3301–25. http://dx.doi.org/10.1175/jcli-d-17-0362.1.

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AbstractLong-term Atmospheric Radiation Measurement (ARM) datasets collected at the three tropical western Pacific (TWP) sites are used to evaluate the ability of the Community Atmosphere Model (CAM5) to simulate the various types of clouds, their seasonal and diurnal variations, and their impact on surface radiation. A number of CAM5 simulations are conducted at various horizontal grid spacing (around 2°, 1°, 0.5°, and 0.25°) with meteorological constraints from analysis or reanalysis. Model biases in the seasonal cycle of cloudiness are found to be weakly dependent on model resolution. Positive biases (up to 20%) in the annual mean total cloud fraction appear mostly in stratiform ice clouds. Higher-resolution simulations do reduce the positive bias in ice clouds, but they inadvertently increase the negative biases in convective clouds and low-level liquid clouds, leading to a positive bias in annual mean shortwave fluxes at the sites, as high as 65 W m−2 in the 0.25° simulation. Such resolution-dependent biases in clouds can adversely lead to biases in ambient thermodynamic properties and, in turn, produce feedback onto clouds. Both the model and observations show distinct diurnal cycles in total, stratiform, and convective cloud fractions; however, they are out of phase by 12 h and the biases vary by site. The results suggest that biases in deep convection affect the vertical distribution and diurnal cycle of stratiform clouds through the transport of vapor and/or the detrainment of liquid and ice. The approach used here can be easily adapted for the evaluation of new parameterizations being developed for CAM5 or other global or regional models.

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You, Cheng, Michael Tjernström, and Abhay Devasthale. "Warm and moist air intrusions into the winter Arctic: a Lagrangian view on the near-surface energy budgets." Atmospheric Chemistry and Physics 22, no. 12 (June 21, 2022): 8037–57. http://dx.doi.org/10.5194/acp-22-8037-2022.

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Abstract. In this study, warm and moist air intrusions (WaMAIs) over the Arctic Ocean sectors of Barents Sea, Kara Sea, Laptev Sea, East Siberian Sea, Chukchi Sea, and Beaufort Sea in 40 recent winters (from 1979 to 2018) are identified from the ERA5 reanalysis using both Eulerian and Lagrangian views. The analysis shows that WaMAIs, fueled by Arctic blocking, cause a relative surface warming and hence a sea-ice reduction by exerting positive anomalies of net thermal irradiances and turbulent fluxes on the surface. Over Arctic Ocean sectors with land-locked sea ice in winter, such as Laptev Sea, East Siberian Sea, Chukchi Sea, and Beaufort Sea, the total surface energy-budget is dominated by net thermal irradiance. From a Lagrangian perspective, total water path (TWP) increases linearly with the downstream distance from the sea-ice edge over the completely ice-covered sectors, inducing almost linearly increasing net thermal irradiance and total surface energy-budget. However, over the Barents Sea, with an open ocean to the south, total net surface energy-budget is dominated by the surface turbulent flux. With the energy in the warm-and-moist air continuously transported to the surface, net surface turbulent flux gradually decreases with distance, especially within the first 2∘ north of the ice edge, inducing a decreasing but still positive total surface energy-budget. The boundary-layer energy-budget patterns over the Barents Sea can be categorized into three classes: radiation-dominated, turbulence-dominated, and turbulence-dominated with cold dome, comprising about 52 %, 40 %, and 8 % of all WaMAIs, respectively. Statistically, turbulence-dominated cases with or without cold dome occur along with 1 order of magnitude larger large-scale subsidence than the radiation-dominated cases. For the turbulence-dominated category, larger turbulent fluxes are exerted to the surface, probably because of stronger wind shear. In radiation-dominated WaMAIs, stratocumulus develops more strongly and triggers intensive cloud-top radiative cooling and related buoyant mixing that extends from cloud top to the surface, inducing a thicker well-mixed layer under the cloud. With the existence of cold dome, fewer liquid water clouds were formed, and less or even negative turbulent fluxes could reach the surface.

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Wunch, D., G. C. Toon, P. O. Wennberg, S. C. Wofsy, B. B. Stephens, M. L. Fischer, O. Uchino, et al. "Calibration of the total carbon column observing network using aircraft profile data." Atmospheric Measurement Techniques Discussions 3, no. 3 (June 17, 2010): 2603–32. http://dx.doi.org/10.5194/amtd-3-2603-2010.

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Abstract. The Total Carbon Column Observing Network (TCCON) produces precise measurements of the column average dry-air mole fractions of CO2, CO, CH4, N2O and H2O at a variety of sites worldwide. These observations rely on spectroscopic parameters that are not known with sufficient accuracy to compute total columns that can be used in combination with in situ measurements. The TCCON must therefore be calibrated to World Meteorological Organization (WMO) in situ trace gas measurement scales. We present a calibration of TCCON data using WMO-scale instrumentation aboard aircraft that measured profiles over four TCCON stations during 2008 and 2009. The aircraft campaigns are the Stratosphere-Troposphere Analyses of Regional Transport 2008 (START-08), which included a profile over the Park Falls site, the HIAPER Pole-to-Pole Observations (HIPPO-1) campaign, which included profiles over the Lamont and Lauder sites, a series of Learjet profiles over the Lamont site, and a Beechcraft King Air profile over the Tsukuba site. These calibrations are compared with similar observations made during the INTEX-NA (2004), COBRA-ME (2004) and TWP-ICE (2006) campaigns. A single, global calibration factor for each gas accurately captures the TCCON total column data within error.

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Caine, Simon, Todd P. Lane, Peter T. May, Christian Jakob, Steven T. Siems, Michael J. Manton, and James Pinto. "Statistical Assessment of Tropical Convection-Permitting Model Simulations Using a Cell-Tracking Algorithm." Monthly Weather Review 141, no. 2 (February 1, 2013): 557–81. http://dx.doi.org/10.1175/mwr-d-11-00274.1.

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Abstract This study presents a method for comparing convection-permitting model simulations to radar observations using an innovative object-based approach. The method uses the automated cell-tracking algorithm, Thunderstorm Identification Tracking Analysis and Nowcasting (TITAN), to identify individual convective cells and determine their properties. Cell properties are identified in the same way for model and radar data, facilitating comparison of their statistical distributions. The method is applied to simulations of tropical convection during the Tropical Warm Pool-International Cloud Experiment (TWP-ICE) using the Weather Research and Forecasting Model, and compared to data from a ground-based radar. Simulations with different microphysics and model resolution are also conducted. Among other things, the comparisons between the model and the radar elucidate model errors in the depth and size of convective cells. On average, simulated convective cells reached higher altitudes than the observations. Also, when using a low reflectivity (25 dBZ) threshold to define convective cells, the model underestimates the size of the largest cells in the observed population. Some of these differences are alleviated with a change of microphysics scheme and higher model resolution, demonstrating the utility of this method for assessing model changes.

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Roskovensky, J. K., and K. N. Liou. "Simultaneous Determination of Aerosol and Thin Cirrus Optical Depths over Oceans from MODIS Data: Some Case Studies." Journal of the Atmospheric Sciences 63, no. 9 (September 1, 2006): 2307–23. http://dx.doi.org/10.1175/jas3747.1.

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Abstract The importance of separating thin cirrus and aerosols from satellite remote sensing to produce broader and more accurate fields for the determination of respective radiative forcings is highlighted. This has been accomplished through the development of a new methodology for retrieving both thin cirrus and aerosol optical depths simultaneously over oceans from the Moderate Resolution Imaging Spectroradiometer (MODIS) data. This method employs a procedure to quantify and remove the thin cirrus contribution to the observed reflectance through a correlation of visible and 1.38-μm reflectances so that the aerosol signal can be extracted. Aerosol optical depths are then retrieved through comparisons with the simulated reflectances created a priori. Using the aerosol optical depth along with the specific viewing geometry and surface reflectance as pointers to locations in a lookup table of modeled reflectances, cirrus optical depth and an effective ice crystal size can be retrieved. An iterative scheme has been created that uses the retrieved effective cirrus ice crystal size to account for the effect that the particle size distribution has on the correlation of visible and 1.38-μm reflectance. Retrievals of both aerosol and thin cirrus optical depths over the Atmospheric Radiation Measurement (ARM) Tropical Western Pacific (TWP) site of Nauru performed on a limited number of cases have proven to be consistent with values determined from ground measurements. Also, comparisons with the MODIS aerosol retrievals over a broad area of ocean have highlighted the potential usefulness of this procedure in increasing the amount of potential aerosol information recovered and removing the ever-present thin cirrus contamination.

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Kalesse, Heike, and Pavlos Kollias. "Climatology of High Cloud Dynamics Using Profiling ARM Doppler Radar Observations." Journal of Climate 26, no. 17 (August 23, 2013): 6340–59. http://dx.doi.org/10.1175/jcli-d-12-00695.1.

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Abstract Ice cloud properties are influenced by cloud-scale vertical air motion. Dynamical properties of ice clouds can be determined via Doppler measurements from ground-based, profiling cloud radars. Here, the decomposition of the Doppler velocities into reflectivity-weighted particle velocity Vt and vertical air motion w is described. The methodology is applied to high clouds observations from 35-GHz profiling millimeter wavelength radars at the Atmospheric Radiation Measurement Program (ARM) Southern Great Plains (SGP) climate research facility in Oklahoma (January 1997–December 2010) and the ARM Tropical Western Pacific (TWP) site in Manus (July 1999–December 2010). The Doppler velocity measurements are used to detect gravity waves (GW), whose correlation with high cloud macrophysical properties is investigated. Cloud turbulence is studied in the absence and presence of GW. High clouds are less turbulent when GW are observed. Probability density functions of Vt, w, and high cloud macrophysical properties for the two cloud subsets (with and without GW) are presented. Air-density-corrected Vt for high clouds for which GW (no GW) were detected amounted to hourly means and standard deviations of 0.89 ± 0.52 m s−1 (0.8 ± 0.48 m s−1) and 1.03 ± 0.41 m s−1 (0.86 ± 0.49 m s−1) at SGP and Manus, respectively. The error of w at one standard deviation was estimated as 0.15 m s−1. Hourly means of w averaged around 0 m s−1 with standard deviations of ±0.27 (SGP) and ±0.29 m s−1 (Manus) for high clouds without GW and ±0.22 m s−1 (both sites) for high clouds with GW. The midlatitude site showed stronger seasonality in detected high cloud properties.

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Journal articles on the topic 'TWP-ICE'

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