scholarly journals Assessing the Vertical Latent Heating Structure of the East Pacific ITCZ Using the CloudSat CPR and TRMM PR

2018 ◽  
Vol 31 (7) ◽  
pp. 2563-2577 ◽  
Author(s):  
L. Huaman ◽  
C. Schumacher
Keyword(s):  
Meridional Circulation ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Hadley Cell ◽  
Convective Precipitation ◽  
Latent Heating ◽  
Shallow Convection ◽  
East Pacific ◽  
Trmm Pr ◽  
Heating Profiles

In the east Pacific (EP) intertropical convergence zone (ITCZ), Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) latent heating retrievals suggest a top-heavy structure; however, light precipitation and its associated low-level heating are underestimated by the PR. This study uses stratiform and deep convective precipitation from the TRMM PR and shallow precipitation from the more sensitive CloudSat radar to assess the seasonal latent heating structure in the EP ITCZ (130°–90°W) for 1998–2014. This study also uses reanalyses (MERRA-2, ERA-Interim, and NCEP–NCAR) to analyze the meridional circulation linked to variations in ITCZ heating. The TRMM/ CloudSat heating profiles suggest a distinct seasonality. During DJF, latent heating peaks at 800 hPa because of the predominance of shallow convection and rises to 700 hPa during MAM as the contribution from deep convective rain increases. During JJA and SON, stratiform precipitation increases and the latent heating has a double peak at 700 and 400 hPa. Additionally, the EP ITCZ heating has a meridional slope throughout most of the year as a result of the prevalence of shallow (deep) convection in the southern (northern) part of the ITCZ. While the reanalyses agree that the most bottom-heavy heating occurs in DJF and the most top-heavy heating occurs in JJA, they underestimate heating aloft compared to the satellite retrievals throughout the year and show varying ability in representing the shallow meridional circulation and deeper Hadley cell overturning.

Effect of Convective Entrainment/Detrainment on the Simulation of the Tropical Precipitation Diurnal Cycle*

2007 ◽  
Vol 135 (2) ◽  
pp. 567-585 ◽  
Author(s):  
Yuqing Wang ◽  
Li Zhou ◽  
Kevin Hamilton
Keyword(s):  
Diurnal Cycle ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Atmospheric Model ◽  
Convective Precipitation ◽  
Shallow Convection ◽  
Eddy Simulation ◽  
Mature Phase ◽  
Diurnal Range ◽  
Convective Parameterization Scheme

Abstract A regional atmospheric model (RegCM) developed at the International Pacific Research Center (IPRC) is used to investigate the effect of assumed fractional convective entrainment/detrainment rates in the Tiedtke mass flux convective parameterization scheme on the simulated diurnal cycle of precipitation over the Maritime Continent region. Results are compared with observations based on 7 yr of the Tropical Rainfall Measuring Mission (TRMM) satellite measurements. In a control experiment with the default fractional convective entrainment/detrainment rates, the model produces results typical of most other current regional and global atmospheric models, namely a diurnal cycle with precipitation rates over land that peak too early in the day and with an unrealistically large diurnal range. Two sensitivity experiments were conducted in which the fractional entrainment/detrainment rates were increased in the deep and shallow convection parameterizations, respectively. Both of these modifications slightly delay the time of the rainfall-rate peak during the day and reduce the diurnal amplitude of precipitation, thus improving the simulation of precipitation diurnal cycle to some degree, but better results are obtained when the assumed entrainment/detrainment rates for shallow convection are increased to the value consistent with the published results from a large eddy simulation (LES) study. It is shown that increasing the entrainment/detrainment rates would prolong the development and reduce the strength of deep convection, thus delaying the mature phase and reducing the amplitude of the convective precipitation diurnal cycle over the land. In addition to the improvement in the simulation of the precipitation diurnal cycle, convective entrainment/detrainment rates also affect the simulation of temporal variability of daily mean precipitation and the partitioning of stratiform and convective rainfall in the model. The simulation of the observed offshore migration of the diurnal signal is realistic in some regions but is poor in some other regions. This discrepancy seems not to be related to the convective lateral entrainment/detrainment rate but could be due to the insufficient model resolution used in this study that is too coarse to resolve the complex land–sea contrast.

Distributions of Shallow to Very Deep Precipitation–Convection in Rapidly Intensifying Tropical Cyclones

2015 ◽  
Vol 28 (22) ◽  
pp. 8791-8824 ◽  
Author(s):  
Cheng Tao ◽  
Haiyan Jiang
Keyword(s):  
Tropical Cyclones ◽  
Inner Core ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Intensity Change ◽  
Latent Heating ◽  
Precipitation Radar ◽  
Trmm Pr ◽  
Radar Echo ◽  
Trmm Precipitation

Abstract Shear-relative distributions of four types of precipitation/convection in tropical cyclones (TCs) are statistically analyzed using 14 years of Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) data. The dataset of 1139 TRMM PR overpasses of tropical storms through category-2 hurricanes over global TC-prone basins is divided by future 24-h intensity change. It is found that increased and widespread shallow precipitation (defined as where the 20-dBZ radar echo height <6 km) around the storm center is a first sign of rapid intensification (RI) and could be used as a predictor of the onset of RI. The contribution to total volumetric rain and latent heating from shallow and moderate precipitation (20-dBZ echo height between 6 and 10 km) in the inner core is greater in RI storms than in non-RI storms, while the opposite is true for moderately deep (20-dBZ echo height between 10 and 14 km) and very deep precipitation (20-dBZ echo height ≥14 km). The authors argue that RI is more likely triggered by the increase of shallow–moderate precipitation and the appearance of more moderately to very deep convection in the middle of RI is more likely a response or positive feedback to changes in the vortex. For RI storms, a cyclonic rotation of frequency peaks from shallow (downshear right) to moderate (downshear left) to moderately and very deep precipitation (upshear left) is found and may be an indicator of a rapidly strengthening vortex. A ring of almost 90% occurrence of total precipitation is found for storms in the middle of RI, consistent with the previous finding of the cyan and pink ring on the 37-GHz color product.

scholarly journals On the Land–Ocean Contrast of Tropical Convection and Microphysics Statistics Derived from TRMM Satellite Signals and Global Storm-Resolving Models

2016 ◽  
Vol 17 (5) ◽  
pp. 1425-1445 ◽  
Author(s):  
Toshi Matsui ◽  
Jiun-Dar Chern ◽  
Wei-Kuo Tao ◽  
Stephen Lang ◽  
Masaki Satoh ◽  
...  
Keyword(s):  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Atmospheric Model ◽  
Evaluation Framework ◽  
Convective Precipitation ◽  
Modeling Framework ◽  
Near Surface ◽  
Microwave Scattering ◽  
Microwave Imager ◽  
Multiscale Modeling Framework

Abstract A 14-yr climatology of Tropical Rainfall Measuring Mission (TRMM) collocated multisensor signal statistics reveals a distinct land–ocean contrast as well as geographical variability of precipitation type, intensity, and microphysics. Microphysics information inferred from the TRMM Precipitation Radar and Microwave Imager show a large land–ocean contrast for the deep category, suggesting continental convective vigor. Over land, TRMM shows higher echo-top heights and larger maximum echoes, suggesting taller storms and more intense precipitation, as well as larger microwave scattering, suggesting the presence of more/larger frozen convective hydrometeors. This strong land–ocean contrast in deep convection is invariant over seasonal and multiyear time scales. Consequently, relatively short-term simulations from two global storm-resolving models can be evaluated in terms of their land–ocean statistics using the TRMM Triple-Sensor Three-Step Evaluation Framework via a satellite simulator. The models evaluated are the NASA Multiscale Modeling Framework (MMF) and the Nonhydrostatic Icosahedral Cloud Atmospheric Model (NICAM). While both simulations can represent convective land–ocean contrasts in warm precipitation to some extent, near-surface conditions over land are relatively moister in NICAM than MMF, which appears to be the key driver in the divergent warm precipitation results between the two models. Both the MMF and NICAM produced similar frequencies of large CAPE between land and ocean. The dry MMF boundary layer enhanced microwave scattering signals over land, but only NICAM had an enhanced deep convection frequency over land. Neither model could reproduce a realistic land–ocean contrast in deep convective precipitation microphysics. A realistic contrast between land and ocean remains an issue in global storm-resolving modeling.

Spectral Retrieval of Latent Heating Profiles from TRMM PR Data. Part IV: Comparisons of Lookup Tables from Two- and Three-Dimensional Cloud-Resolving Model Simulations

2009 ◽  
Vol 22 (20) ◽  
pp. 5577-5594 ◽  
Author(s):  
Shoichi Shige ◽  
Yukari N. Takayabu ◽  
Satoshi Kida ◽  
Wei-Kuo Tao ◽  
Xiping Zeng ◽  
...  
Keyword(s):  
Three Dimensional ◽  
Latent Heating ◽  
3D Simulations ◽  
Toga Coare ◽  
Trmm Pr ◽  
Lookup Tables ◽  
Cloud Resolving Model ◽  
Heating Profiles ◽  
Maximum Heating ◽  
Melting Level

Abstract The spectral latent heating (SLH) algorithm was developed to estimate latent heating profiles for the Tropical Rainfall Measuring Mission Precipitation Radar (TRMM PR). The method uses TRMM PR information (precipitation-top height, precipitation rates at the surface and melting level, and rain type) to select heating profiles from lookup tables (LUTs). LUTs for the three rain types—convective, shallow stratiform, and anvil rain (deep stratiform with a melting level)—were derived from numerical simulations of tropical cloud systems from the Tropical Ocean and Global Atmosphere Coupled Ocean–Atmosphere Response Experiment (TOGA COARE) using a cloud-resolving model (CRM). The two-dimensional (2D) CRM was used in previous studies. The availability of exponentially increasing computer capabilities has resulted in three-dimensional (3D) CRM simulations for multiday periods becoming increasingly prevalent. In this study, LUTs from the 2D and 3D simulations are compared. Using the LUTs from 3D simulations results in less agreement between the SLH-retrieved heating and sounding-based heating for the South China Sea Monsoon Experiment (SCSMEX). The level of SLH-estimated maximum heating is lower than that of the sounding-derived maximum heating. This is explained by the fact that using the 3D LUTs results in stronger convective heating and weaker stratiform heating above the melting level than is the case if using the 2D LUTs. More condensate is generated in and carried from the convective region in the 3D model than in the 2D model, and less condensate is produced by the stratiform region’s own upward motion.

scholarly journals Simulating deep convection with a shallow convection scheme

2011 ◽  
Vol 11 (20) ◽  
pp. 10389-10406 ◽  
Author(s):  
C. Hohenegger ◽  
C. S. Bretherton
Keyword(s):  
Climate Modeling ◽  
Global Climate ◽  
Deep Convection ◽  
Convective Precipitation ◽  
Cloud Base ◽  
Gradual Transition ◽  
Shallow Convection ◽  
Convection Scheme ◽  
Community Atmosphere Model ◽  
Simulated Precipitation

Abstract. Convective processes profoundly affect the global water and energy balance of our planet but remain a challenge for global climate modeling. Here we develop and investigate the suitability of a unified convection scheme, capable of handling both shallow and deep convection, to simulate cases of tropical oceanic convection, mid-latitude continental convection, and maritime shallow convection. To that aim, we employ large-eddy simulations (LES) as a benchmark to test and refine a unified convection scheme implemented in the Single-column Community Atmosphere Model (SCAM). Our approach is motivated by previous cloud-resolving modeling studies, which have documented the gradual transition between shallow and deep convection and its possible importance for the simulated precipitation diurnal cycle. Analysis of the LES reveals that differences between shallow and deep convection, regarding cloud-base properties as well as entrainment/detrainment rates, can be related to the evaporation of precipitation. Parameterizing such effects and accordingly modifying the University of Washington shallow convection scheme, it is found that the new unified scheme can represent both shallow and deep convection as well as tropical and mid-latitude continental convection. Compared to the default SCAM version, the new scheme especially improves relative humidity, cloud cover and mass flux profiles. The new unified scheme also removes the well-known too early onset and peak of convective precipitation over mid-latitude continental areas.

scholarly journals Local Balance and Variability of Atmospheric Heat Budget over Oceans: Observation and Reanalysis-Based Estimates

2014 ◽  
Vol 27 (2) ◽  
pp. 893-913 ◽  
Author(s):  
Sun Wong ◽  
Tristan S. L’Ecuyer ◽  
William S. Olson ◽  
Xianan Jiang ◽  
Eric J. Fetzer
Keyword(s):  
Heat Budget ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Heat Fluxes ◽  
Radiative Heating ◽  
Latent Heating ◽  
Heating Rates ◽  
Cooling Rates ◽  
Atmospheric Heating ◽  
Atmospheric Heat

Abstract The authors quantify systematic differences between modern observation- and reanalysis-based estimates of atmospheric heating rates and identify dominant variability modes over tropical oceans. Convergence of heat fluxes between the top of the atmosphere and the surface are calculated over the oceans using satellite-based radiative and sensible heat fluxes and latent heating from precipitation estimates. The convergence is then compared with column-integrated atmospheric heating based on Tropical Rainfall Measuring Mission data as well as the heating calculated using temperatures from the Atmospheric Infrared Sounder and wind fields from the Modern-Era Retrospective Analysis for Research and Applications (MERRA). Corresponding calculations using MERRA and the European Centre for Medium-Range Weather Forecasts Interim Re-Analysis heating rates and heat fluxes are also performed. The geographical patterns of atmospheric heating rates show heating regimes over the intertropical convergence zone and summertime monsoons and cooling regimes over subsidence areas in the subtropical oceans. Compared to observation-based datasets, the reanalyses have larger atmospheric heating rates in heating regimes and smaller cooling rates in cooling regimes. For the averaged heating rates over the oceans in 40°S–40°N, the observation-based datasets have net atmospheric cooling rates (from −15 to −22 W m−2) compared to the reanalyses net warming rates (5.0–5.2 W m−2). This discrepancy implies different pictures of atmospheric heat transport. Wavelet spectra of atmospheric heating rates show distinct maxima of variability in annual, semiannual, and/or intraseasonal time scales. In regimes where deep convection frequently occurs, variability is mainly driven by latent heating. In the subtropical subsidence areas, variability in radiative heating is comparable to that in latent heating.

scholarly journals Shallow and Deep Latent Heating Modes over Tropical Oceans Observed with TRMM PR Spectral Latent Heating Data

2010 ◽  
Vol 23 (8) ◽  
pp. 2030-2046 ◽  
Author(s):  
Yukari N. Takayabu ◽  
Shoichi Shige ◽  
Wei-Kuo Tao ◽  
Nagio Hirota
Keyword(s):  
Large Scale ◽  
Deep Convection ◽  
Three Dimensional ◽  
Tropical Rainfall Measuring Mission ◽  
Radiative Heating ◽  
Latent Heating ◽  
Tropical Oceans ◽  
Trmm Precipitation ◽  
Subtropical Oceans ◽  
Cumulus Congestus

Abstract Three-dimensional distributions of the apparent heat source (Q1) − radiative heating (QR) estimated from Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) utilizing the spectral latent heating (SLH) algorithm are analyzed. Mass-weighted and vertically integrated Q1 − QR averaged over the tropical oceans is estimated as ∼72.6 J s−1 (∼2.51 mm day−1) and that over tropical land is ∼73.7 J s−1 (∼2.55 mm day−1) for 30°N–30°S. It is shown that nondrizzle precipitation over tropical and subtropical oceans consists of two dominant modes of rainfall systems: deep systems and congestus. A rough estimate of the shallow-heating contribution against the total heating is about 46.7% for the average tropical oceans, which is substantially larger than the 23.7% over tropical land. Although cumulus congestus heating linearly correlates with SST, deep-mode heating is dynamically bounded by large-scale subsidence. It is notable that a substantial amount of rain, as large as 2.38 mm day−1 on average, is brought from congestus clouds under the large-scale subsiding circulation. It is also notable that, even in the region with SSTs warmer than 28°C, large-scale subsidence effectively suppresses the deep convection, with the remaining heating by congestus clouds. The results support that the entrainment of mid–lower-tropospheric dry air, which accompanies the large-scale subsidence, is the major factor suppressing the deep convection. Therefore, a representation of the realistic entrainment is very important for proper reproduction of precipitation distribution and the resultant large-scale circulation.

scholarly journals Idealized Large-Eddy and Convection-Resolving Simulations of Moist Convection over Mountainous Terrain

2016 ◽  
Vol 73 (10) ◽  
pp. 4021-4041 ◽  
Author(s):  
Davide Panosetti ◽  
Steven Böing ◽  
Linda Schlemmer ◽  
Jürg Schmidli
Keyword(s):  
Deep Convection ◽  
Convective Precipitation ◽  
Scale Model ◽  
Mountainous Terrain ◽  
Moist Convection ◽  
Shallow Convection ◽  
Large Eddy ◽  
Thermally Driven ◽  
Convection Initiation ◽  
Horizontal Grid

Abstract On summertime fair-weather days, thermally driven wind systems play an important role in determining the initiation of convection and the occurrence of localized precipitation episodes over mountainous terrain. This study compares the mechanisms of convection initiation and precipitation development within a thermally driven flow over an idealized double-ridge system in large-eddy (LESs) and convection-resolving (CRM) simulations. First, LES at a horizontal grid spacing of 200 m is employed to analyze the developing circulations and associated clouds and precipitation. Second, CRM simulations at horizontal grid length of 1 km are conducted to evaluate the performance of a kilometer-scale model in reproducing the discussed mechanisms. Mass convergence and a weaker inhibition over the two ridges flanking the valley combine with water vapor advection by upslope winds to initiate deep convection. In the CRM simulations, the spatial distribution of clouds and precipitation is generally well captured. However, if the mountains are high enough to force the thermally driven flow into an elevated mixed layer, the transition to deep convection occurs faster, precipitation is generated earlier, and surface rainfall rates are higher compared to the LES. Vertical turbulent fluxes remain largely unresolved in the CRM simulations and are underestimated by the model, leading to stronger upslope winds and increased horizontal moisture advection toward the mountain summits. The choice of the turbulence scheme and the employment of a shallow convection parameterization in the CRM simulations change the strength of the upslope winds, thereby influencing the simulated timing and intensity of convective precipitation.

scholarly journals The Next-Generation Goddard Convective–Stratiform Heating Algorithm: New Tropical and Warm-Season Retrievals for GPM

2018 ◽  
Vol 31 (15) ◽  
pp. 5997-6026 ◽  
Author(s):  
Stephen E. Lang ◽  
Wei-Kuo Tao
Keyword(s):  
Warm Season ◽  
Tropical Rainfall Measuring Mission ◽  
Shallow Convection ◽  
Heating Rates ◽  
Low Level ◽  
Precipitation Measurement ◽  
Cloud Resolving Model ◽  
Upper Level ◽  
Heating Profiles ◽  
Global Precipitation

The Goddard convective–stratiform heating (CSH) algorithm, used to estimate cloud heating in support of the Tropical Rainfall Measuring Mission (TRMM), is upgraded in support of the Global Precipitation Measurement (GPM) mission. The algorithm’s lookup tables (LUTs) are revised using new and additional cloud-resolving model (CRM) simulations from the Goddard Cumulus Ensemble (GCE) model, producing smoother heating patterns that span a wider range of intensities because of the increased sampling and finer GPM product grid. Low-level stratiform cooling rates are reduced in the land LUTs for a given rain intensity because of the rain evaporation correction in the new four-class ice (4ICE) scheme. Additional criteria, namely, echo-top heights and low-level reflectivity gradients, are tested for the selection of heating profiles. Those resulting LUTs show greater and more precise variation in their depth of heating as well as a tendency for stronger cooling and heating rates when low-level dB Z values decrease toward the surface. Comparisons versus TRMM for a 3-month period show much more low-level heating in the GPM retrievals because of increased detection of shallow convection, while upper-level heating patterns remain similar. The use of echo tops and low-level reflectivity gradients greatly reduces midlevel heating from ~2 to 5 km in the mean GPM heating profile, resulting in a more top-heavy profile like TRMM versus a more bottom-heavy profile with much more midlevel heating. Integrated latent heating rates are much better balanced versus surface rainfall for the GPM retrievals using the additional selection criteria with an overall bias of +4.3%.

Dynamics of the Shallow Meridional Circulation around Intertropical Convergence Zones

2007 ◽  
Vol 64 (7) ◽  
pp. 2262-2285 ◽  
Author(s):  
David S. Nolan ◽  
Chidong Zhang ◽  
Shu-hua Chen
Keyword(s):  
Boundary Layer ◽  
Pressure Gradient ◽  
Meridional Circulation ◽  
Deep Convection ◽  
Hadley Circulation ◽  
Sea Breeze ◽  
Return Flow ◽  
Convective Heating ◽  
Moist Convection ◽  
East Pacific

Abstract The generally accepted view of the meridional circulation in the tropical east Pacific is that of a single deep overturning cell driven by deep convective heating in the intertropical convergence zone (ITCZ), similar to the zonal mean Hadley circulation. However, recent observations of the atmosphere from the tropical eastern Pacific have called this view into question. In several independent datasets, significant meridional return flows out of the ITCZ region were observed, not only at high altitudes, but also at low altitudes, just above the atmospheric boundary layer. This paper presents a theory and idealized simulations to understand the causes and dynamics of this shallow meridional circulation (SMC). Fundamentally, the SMC can be seen as a large-scale sea-breeze circulation driven by sea surface temperature gradients when deep convection is absent in the ITCZ region. A simple model of this circulation is presented. Using observed values, the sea-breeze model shows that the pressure gradient above the boundary can indeed reverse, leading to the pressure force that drives the shallow return flow out of the ITCZ. The Weather Research and Forecast Model (WRF) is used to simulate an idealized Hadley circulation driven by moist convection in a tropical channel. The SMC is reproduced, with reasonable similarity to the circulation observed in the east Pacific. The simulations confirm that the SMC is driven by a reversal of the pressure gradient above the boundary layer, and that the return flow is strongest when deep convection is absent in the ITCZ, and weakest when deep convection is active. The model also shows that moisture transport out of the ITCZ region is far greater in the low-level shallow return flow than in the high-altitude return flow associated with the deep overturning, and that a budget for water transport in and out of the ITCZ region is grossly incomplete without it. Much of the moisture carried in the shallow return flow is recycled into the boundary layer, but does not appear to contribute to enhanced cloudiness in the subtropical stratocumulus poleward of the ITCZ.

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