Rainfall, Convection, and Latent Heating Distributions in Rapidly Intensifying Tropical Cyclones

2014 ◽  
Vol 71 (8) ◽  
pp. 2789-2809 ◽  
Author(s):  
Joseph P. Zagrodnik ◽  
Haiyan Jiang
Keyword(s):  
Deep Convection ◽  
Vertical Wind Shear ◽  
Tropical Rainfall Measuring Mission ◽  
Intensity Change ◽  
Shear Direction ◽  
Latent Heating ◽  
Strongly Correlated ◽  
Near Surface ◽  
Rainfall Frequency ◽  
Trmm Precipitation

Abstract Tropical cyclone (TC) rainfall, convection, and latent heating distributions are compiled from 14 years of Tropical Rainfall Measuring Mission (TRMM) precipitation radar overpasses. The dataset of 818 Northern Hemisphere tropical storms through category 2 hurricanes is divided by future 24-h intensity change and exclusively includes storms with at least moderately favorable environmental conditions. The rapidly intensifying (RI) category is further subdivided into an initial [RI (initial)] and continuing [RI (continuing)] category based on whether the storm is near the beginning of an RI event or has already been undergoing RI for 12 or more hours prior to the TRMM overpass. TCs in each intensity change category are combined into composite diagrams orientated relative to the environmental vertical wind shear direction. Rainfall frequency, defined as the shear-relative occurrence of PR near-surface reflectivity >20 dBZ, is most strongly correlated with future intensity change. The rainfall frequency is also higher in RI (continuing) TCs than RI (initial). Moderate-to-deep convection and latent heating only increase significantly after RI is underway for at least 12 h in the innermost 50 km relative to the TC center. The additional precipitation in rapidly intensifying TCs is composed primarily of a mixture of weak convective and stratiform rain, especially in the upshear quadrants. The rainfall frequency and latent heating distributions are more symmetric near the onset of RI and continue to become more symmetric as RI continues and the rainfall coverage expands upshear. The relationship between rainfall distributions and future TC intensity highlights the potential of 37-GHz satellite imagery to improve real-time intensity forecasting.

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 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 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.

scholarly journals Precipitation Clouds Delineation Scheme in Tropical Cyclones and Its Validation Using Precipitation and Cloud Parameter Datasets from TRMM

2018 ◽  
Vol 57 (4) ◽  
pp. 821-836 ◽  
Author(s):  
FengJiao Chen ◽  
ShaoXue Sheng ◽  
ZhengQing Bao ◽  
HuaYang Wen ◽  
LianSheng Hua ◽  
...  
Keyword(s):  
Tropical Cyclones ◽  
Tropical Rainfall Measuring Mission ◽  
Probability Of Detection ◽  
Liquid Water Path ◽  
Near Surface ◽  
Cloud Parameters ◽  
Infrared Measurements ◽  
Trmm Precipitation ◽  
Cloud Parameter ◽  
Probability Of Precipitation

AbstractUtilizing the cloud parameters derived from the Tropical Rainfall Measuring Mission (TRMM) Visible and Infrared Scanner and the near-surface rainfall detected by the TRMM Precipitation Radar, the differences of cloud parameters for precipitating clouds (PCs) and nonprecipitating clouds (NPCs) are examined in tropical cyclones (TCs) during daytime from June to September 1998–2010. A precipitation delineation scheme that is based on cloud parameter thresholds is proposed and validated using the independent TC datasets in 2011 and observational datasets from Terra/MODIS. Statistical analysis of these results shows that the differences in the effective radius of cloud particles Re are small for PCs and NPCs, while thick clouds with large cloud optical thickness (COT) and liquid water path (LWP) can be considered as candidates for PCs. The probability of precipitation increases rapidly as the LWP and COT increase, reaching ~90%, whereas the probability of precipitation reaches a peak value of only 30% as Re increases. The combined threshold of a brightness temperature at 10.8 μm (BT4) of 270 K and an LWP of 750 g m−2 shows the best performance for precipitation discrimination at the pixel levels, with the probability of detection (POD) reaching 68.2% and false-alarm ratio (FAR) reaching 31.54%. From MODIS observations, the composite scheme utilizing BT4 and LWP also proves to be a good index, with POD reaching 77.39% and FAR reaching 24.2%. The results from this study demonstrate a potential application of real-time precipitation monitoring in TCs utilizing cloud parameters from visible and infrared measurements on board geostationary weather satellites.

scholarly journals Mesoscale Vortex Development during Extreme Precipitation: Colorado, September 2013

2015 ◽  
Vol 143 (12) ◽  
pp. 4943-4962 ◽  
Author(s):  
Annareli Morales ◽  
Russ S. Schumacher ◽  
Sonia M. Kreidenweis
Keyword(s):  
Deep Convection ◽  
Vortex Formation ◽  
Vertical Gradient ◽  
Cloud Water ◽  
Latent Heating ◽  
Near Surface ◽  
Water Condensation ◽  
Mesoscale Convective ◽  
Arw Model ◽  
Lee Vortex

Abstract On 11–12 September 2013, portions of northern Colorado experienced flash flooding as a result of high rain rates accumulating over 180 mm of rain in 6 h. From 0400 to 0700 UTC 12 September a mesovortex was observed traveling northwestward toward the city of Boulder, Colorado, with enhanced upslope flow on its north side and localized deep convection. Although the mesovortex was observed in an area common for lee vortex formation, namely that associated with the Denver Cyclone, it is shown via ARW model simulations that the mesovortex intensified through the release of latent heat, similar to the processes leading to mesoscale convective vortices, rather than by dry topographic-flow dynamics. High rates of cloud water condensation at relatively low altitudes led to a strong vertical gradient in latent heating, resulting in a near-surface positive potential vorticity anomaly. Reducing the contribution of cloud water condensation to latent heating by 50% resulted in no mesovortex development in the model and a substantial decrease in precipitation. On the other hand, removing the topographical forcing in the model did not inhibit the mesovortex formation, confirming the secondary role of topography. The mesovortex enhanced upslope winds and convection, and was thus a key feature in the generation of intense precipitation over Boulder. The ability to forecast the development of these mesovortices and their subsequent environmental and hydrological effects could be critical for decision-makers and the public, given their association with high rainfall rates.

Contribution of Tropical Cyclones to Global Very Deep Convection

2014 ◽  
Vol 27 (11) ◽  
pp. 4313-4336 ◽  
Author(s):  
Haiyan Jiang ◽  
Cheng Tao
Keyword(s):  
Tropical Cyclones ◽  
Deep Convection ◽  
Convective Available Potential Energy ◽  
Tropical Rainfall Measuring Mission ◽  
Precipitable Water ◽  
Moisture Exchange ◽  
Derived Properties ◽  
Trmm Precipitation ◽  
The Tropics ◽  
Heat And Moisture

Abstract Based on the 12-yr (1998–2009) Tropical Rainfall Measuring Mission (TRMM) precipitation feature (PF) database, both radar and infrared (IR) observations from TRMM are used to quantify the contribution of tropical cyclones (TCs) to very deep convection (VDC) in the tropics and to compare TRMM-derived properties of VDC in TCs and non-TCs. Using a radar-based definition, it is found that the contribution of TCs to total VDC in the tropics is not much higher than the contribution of TCs to total PFs. However, the area-based contribution of TCs to overshooting convection defined by IR is 13.3%, which is much higher than the 3.2% contribution of TCs to total PFs. This helps explain the contradictory results between previous radar-based and IR-based studies and indicates that TCs only contribute disproportionately large amount of overshooting convection containing mainly small ice particles that are barely detected by the TRMM radar. VDC in non-TCs over land has the highest maximum 30- and 40-dBZ height and the strongest ice-scattering signature derived from microwave 85- and 37-GHz observations, while VDC in TCs has the coldest minimum IR brightness temperature and largest overshooting distance and area. This suggests that convection is much more intense in non-TCs over land but is much deeper or colder in TCs. It is found that VDC in TCs usually has smaller environmental shear but larger total precipitable water and convective available potential energy than those in non-TCs. These findings offer evidence that TCs may contribute disproportionately to troposphere-to-stratosphere heat and moisture exchange.

Assessing the Influence of Convective Downdrafts and Surface Enthalpy Fluxes on Tropical Cyclone Intensity Change in Moderate Vertical Wind Shear

2019 ◽  
Vol 147 (10) ◽  
pp. 3519-3534 ◽  
Author(s):  
Leon T. Nguyen ◽  
Robert Rogers ◽  
Jonathan Zawislak ◽  
Jun A. Zhang
Keyword(s):  
Boundary Layer ◽  
Wind Shear ◽  
Deep Convection ◽  
Vertical Wind Shear ◽  
Lower Troposphere ◽  
Observation Time ◽  
Vertical Wind ◽  
Intensity Change ◽  
Conditional Instability ◽  
Surface Enthalpy

Abstract The thermodynamic impacts of downdraft-induced cooling/drying and downstream recovery via surface enthalpy fluxes within tropical cyclones (TCs) were investigated using dropsonde observations collected from 1996 to 2017. This study focused on relatively weak TCs (tropical depression, tropical storm, category 1 hurricane) that were subjected to moderate (4.5–11.0 m s−1) levels of environmental vertical wind shear. The dropsonde data were analyzed in a shear-relative framework and binned according to TC intensity change in the 24 h following the dropsonde observation time, allowing for comparison between storms that underwent different intensity changes. Moisture and temperature asymmetries in the lower troposphere yielded a relative maximum in lower-tropospheric conditional instability in the downshear quadrants and a relative minimum in instability in the upshear quadrants, regardless of intensity change. However, the instability increased as the intensification rate increased, particularly in the downshear quadrants. This was due to increased boundary layer moist entropy relative to the temperature profile above the boundary layer. Additionally, significantly larger surface enthalpy fluxes were observed as the intensification rate increased, particularly in the upshear quadrants. These results suggest that in intensifying storms, enhanced surface enthalpy fluxes in the upshear quadrants allow downdraft-modified boundary layer air to recover moisture and heat more effectively as it is advected cyclonically around the storm. By the time the air reaches the downshear quadrants, the lower-tropospheric conditional instability is enhanced, which is speculated to be more favorable for updraft growth and deep convection.

“Warm Rain” in the Tropics: Seasonal and Regional Distributions Based on 9 yr of TRMM Data

2009 ◽  
Vol 22 (3) ◽  
pp. 767-779 ◽  
Author(s):  
Chuntao Liu ◽  
Edward J. Zipser
Keyword(s):  
Tropical Rainfall Measuring Mission ◽  
Precipitation Radar ◽  
Near Surface ◽  
Freezing Level ◽  
Tropical Oceans ◽  
Warm Rain ◽  
Seasonal And Diurnal Variations ◽  
Radar Echo ◽  
Trmm Precipitation ◽  
The Tropics

Abstract How much precipitation is contributed by warm rain systems over the tropics? What is the typical size, intensity, and echo top of warm rain events observed by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar over different regions of the tropics? What proportion of warm raining areas is actually attached to the edges of cold systems? Are there mesoscale warm raining systems, and if so, where and when do they occur? To answer these questions, a 9-yr TRMM precipitation feature database is used in this study. First, warm rain features in 20°S–20°N are selected by specifying precipitation features 1) with minimum infrared brightness temperature > 0°C, 2) with TRMM Precipitation Radar (PR) echo top below freezing level, or 3) without any ice-scattering signature in the microwave observations, respectively. Then, the geographical, seasonal, and diurnal variations of the rain volume inside warm rain features defined in these three ways are presented. The characteristics of warm rain features are summarized. Raining pixels with cloud-top temperature above 0°C contribute 20% of the rainfall over tropical oceans and 7.5% over tropical land. However, about half of the warm pixels over oceans and two-thirds of the warm pixels over land are attached to cold precipitation systems. A large amount of warm rainfall occurs over oceans near windward coasts during winter. Most of the warm rain systems have small size < 100 km2 and weak radar echo with a modal maximum near-surface reflectivity around 23 dBZ. However, mesoscale warm rain systems with strong radar echoes do occur in large regions of the tropical oceans, more during the nighttime than during daytime. Though the mean height of the warm precipitation features over oceans is lower than that over land, there is no significant regional difference in its size and intensity.

scholarly journals Thick Anvils as Viewed by the TRMM Precipitation Radar

2011 ◽  
Vol 24 (6) ◽  
pp. 1718-1735 ◽  
Author(s):  
Wei Li ◽  
Courtney Schumacher
Keyword(s):  
Southern Oscillation ◽  
Deep Convection ◽  
Tropical Rainfall Measuring Mission ◽  
Precipitation Radar ◽  
Central Pacific ◽  
Rain Area ◽  
Areal Coverage ◽  
Trmm Precipitation ◽  
Upper Level ◽  
Highly Correlated

Abstract This study investigates anvils from thick, nonprecipitating clouds associated with deep convection as observed in the tropics by the Tropical Rainfall Measuring Mission (TRMM) Precipitation Radar (PR) during the 10-yr period, 1998–2007. Anvils observable by the PR occur, on average, 5 out of every 100 days within grid boxes with 2.5° resolution and with a conditional areal coverage of 1.5%. Unconditional areal coverage is only a few tenths of a percent. Anvils also had an average 17-dBZ echo top of ∼8.5 km and an average thickness of ∼2.7 km. Anvils were usually higher and thicker over land compared to ocean, and occurred most frequently over Africa, the Maritime Continent, and Panama. Anvil properties were intimately tied to the properties of the parent convection. In particular, anvil area and echo-top heights were highly correlated to convective rain area. The next best predictor for anvil areal coverage and echo tops was convective echo tops, while convective reflectivities had the weakest correlation. Strong upper-level wind shear also may be associated with anvil occurrence over land, especially when convection regularly attains echo-top heights greater than 7 km. Some tropical land regions, especially those affected by monsoon circulations, experience significant seasonal variability in anvil properties—strong interannual anvil variability occurs over the central Pacific because of the El Niño–Southern Oscillation. Compared to the CloudSat Cloud Profiling Radar, the TRMM PR underestimates anvil-top height by an average of ∼5 km and underestimates their horizontal extent by an average factor of 4.

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