scholarly journals A study of evening convective clouds over Kochi and neighbourhood

MAUSAM ◽  
2022 ◽  
Vol 52 (3) ◽  
pp. 463-468
Author(s):  
A. J. MATHEW ◽  
S. U. KAIMAL
Keyword(s):  
Arabian Sea ◽  
El Nino ◽  
Convective Cloud ◽  
Convective Activity ◽  
Convective Clouds ◽  
Post Monsoon ◽  
Radar Echoes ◽  
Sst Anomaly ◽  
The Mean ◽  
Cloud Tops

Radar echoes of 0900 and 1100 UTC over Kochi and 200 km around were studied from 1996 to 1999 along with SST of southeast Arabian Sea and Kochi. The following results are obtained : Monsoon convective cloud tops were lower than Pre-monsoon and Post-monsoon convective cloud tops. (ii) In the mean, monsoon cloud tops gradually increased from 1996 to 1998 and then decreased. (iii) Very large convective activity existed during August 1997 to June 1998 compared to other periods of this study. Seasonally the higher the SST, the higher is convective cloud top. (v) Interannually, large positive SST anomaly coincided with high convective activity and this may be related to then prevailing El Nino.

scholarly journals Improving the Simulation of Tropical Convective Cloud-Top Heights in CAM5 with CloudSat Observations

2018 ◽  
Vol 31 (13) ◽  
pp. 5189-5204 ◽  
Author(s):  
Mingcheng Wang ◽  
Guang J. Zhang
Keyword(s):  
Radiative Forcing ◽  
Model Simulation ◽  
Convective Cloud ◽  
Model Atmosphere ◽  
Convective Precipitation ◽  
Cloud Radiative Forcing ◽  
Convective Clouds ◽  
Community Atmosphere Model ◽  
Cloud Tops ◽  
Main Factor

Using 4 years of CloudSat data, the simulation of tropical convective cloud-top heights (CCTH) above 6 km simulated by the convection scheme in the Community Atmosphere Model, version 5 (CAM5), is evaluated. Compared to CloudSat observations, CAM5 underestimates CCTH by more than 2 km on average. Further analysis of model results suggests that the dilute CAPE calculation, which has been incorporated into the convective parameterization since CAM4, is a main factor restricting CCTH to much lower levels. After removing this restriction, more convective clouds develop into higher altitudes, although convective clouds with tops above 12 km are still underestimated significantly. The environmental conditions under which convection develops in CAM5 are compared with CloudSat observations for convection with similar CCTHs. It is shown that the model atmosphere is much more unstable compared to CloudSat observations, and there is too much entrainment in CAM5. Since CCTHs are closely associated with cloud radiative forcing, the impacts of CCTH on model simulation are further investigated. Results show that the change of CCTH has important impacts on cloud radiative forcing and precipitation. With increased CCTHs, there is more cloud radiative forcing in tropical Africa and the eastern Pacific, but less cloud radiative forcing in the western Pacific. The contribution to total convective precipitation from convection with cloud tops above 9 km is also increased substantially.

scholarly journals Aerosol effects on clouds and precipitation during the 1997 smoke episode in Indonesia

2009 ◽  
Vol 9 (2) ◽  
pp. 743-756 ◽  
Author(s):  
H.-F. Graf ◽  
J. Yang ◽  
T. M. Wagner
Keyword(s):  
Large Scale ◽  
Convective Cloud ◽  
Reanalysis Data ◽  
Cumulus Parameterization ◽  
Convective Precipitation ◽  
Limited Area ◽  
Convective Rainfall ◽  
High Background ◽  
Convective Clouds ◽  
The Mean

Abstract. In 1997/1998 a severe smoke episode due to extensive biomass burning, especially of peat, was observed over Indonesia. September 1997 was the month with the highest aerosol burden. This month was simulated using the limited area model REMOTE driven at its lateral boundaries by ERA40 reanalysis data. REMOTE was extended by a new convective cloud parameterization mimicking individual clouds competing for instability energy. This allows for the interaction of aerosols, convective clouds and precipitation. Results show that in the monthly mean convective precipitation is diminished at nearly all places with high aerosol loading, but at some areas with high background humidity precipitation from large-scale clouds may over-compensate the loss in convective rainfall. The simulations revealed that both large-scale and convective clouds' microphysics are influenced by aerosols. Since aerosols are washed and rained out by rainfall, high aerosol concentrations can only persist at low rainfall rates. Hence, aerosol concentrations are not independent of the rainfall amount and in the mean the maximum absolute effects on rainfall from large scale clouds are found at intermediate aerosol concentrations. The reason for this behavior is that at high aerosol concentrations rainfall rates are small and consequently also the anomalies are small. For large-scale as well as for convective rain negative and positive anomalies are found for all aerosol concentrations. Negative anomalies dominate and are highly statistically significant especially for convective rainfall since part of the precipitation loss from large-scale clouds is compensated by moisture detrained from the convective clouds. The mean precipitation from large-scale clouds is less reduced (however still statistically significant) than rain from convective clouds. This effect is due to detrainment of cloud water from the less strongly raining convective clouds and because of the generally lower absolute amounts of rainfall from large-scale clouds. With increasing aerosol load both, convective and large scale clouds produce less rain. At very few individual time steps cases were found when polluted convective clouds produced intensified rainfall via mixed phase microphysics. However, these cases are not unequivocal and opposite results were also simulated, indicating that other than aerosol-microphysics effects have important impact on the results. Overall, the introduction of the new cumulus parameterization and aerosol-cloud interaction reduced some of the original REMOTE biases of precipitation patterns and total amount.

scholarly journals Tropical, oceanic, deep convective cloud morphology as observed by CloudSat

2015 ◽  
Vol 15 (11) ◽  
pp. 15977-16017 ◽  
Author(s):  
M. R. Igel ◽  
S. C. van den Heever
Keyword(s):  
Convective Cloud ◽  
Data Partitioning ◽  
Width Ratio ◽  
Length Scales ◽  
Morphological Attributes ◽  
Convective Clouds ◽  
Deep Convective Clouds ◽  
Physical Shape ◽  
The Mean ◽  
Upper Level

Abstract. An investigation into the physical shape and size of mature, oceanic, tropical, deep convective clouds is conducted. A previously developed CloudSat data-partitioning methodology is used that separates components of cloud objects and measures their various length scales. In particular, the cloud objects are divided into a lower "pedestal" region on which the upper-level "anvil" region sits. Mean cloud objects are discussed in the framework of this morphological partitioning. For single-core clouds, the mean cloud has an anvil width of 95 km, a pedestal width of 11 km, and an anvil thickness of 6.4 km. The number of identified convective cores within the pedestal correlates positively with certain cloud length scales and morphological attributes of cloud objects such as anvil width. As the number of cores increases, the width of cloud objects is observed to grow. Pedestal width is shown to regress linearly to anvil width when a 2/3rd power scaling is applied to pedestal width. This result implies a decrease in the anvil width to pedestal width ratio with growing pedestals and an equivalence between the mass convected through the pedestal top and that into the anvil. Taller clouds are found to be wider. Some of the results obtained using the CloudSat methodology are also examined with a large-domain radiative-convective equilibrium numerical simulation and are found to exhibit similar trends when modeled. Finally, various CloudSat sampling issues are discussed in several appendices.

Observation of Severe Convective Activity in a Squall Line

1961 ◽  
Vol 42 (4) ◽  
pp. 252-264 ◽  
Author(s):  
George S. McLean
Keyword(s):  
Cross Sections ◽  
Wind Direction ◽  
Squall Line ◽  
Jet Stream ◽  
Convective Activity ◽  
Mean Flow ◽  
The West ◽  
Convective Clouds ◽  
Wet Precipitation ◽  
The Mean

A Project Jet Stream flight into a jet-stream-squall-line situation over Texas on 23 April 1957 is described narratively. Severe turbulence, wet precipitation at −55C, hail and large variations in the wind direction and speed were observed. The latter indicate that strong outflow, associated with the major downdrafts, was superimposed on the mean flow. Vertical motions in excess of 1500 ft per min were measured within the convective clouds. Structure of the jet stream to the west and north of the squall line is described by the use of cross-sections.

scholarly journals Interannual to Diurnal Variations in Tropical and Subtropical Deep Convective Clouds and Convective Overshooting from Seven Years of AMSU-B Measurements

2008 ◽  
Vol 21 (17) ◽  
pp. 4168-4189 ◽  
Author(s):  
Gang Hong ◽  
Georg Heygster ◽  
Justus Notholt ◽  
Stefan A. Buehler
Keyword(s):  
Convective Cloud ◽  
Life Cycles ◽  
Diurnal Variations ◽  
Convergence Zone ◽  
Diurnal Cycles ◽  
Convective Clouds ◽  
Early Evening ◽  
Deep Convective Clouds ◽  
The Mean ◽  
Deep Convective Cloud

Abstract This study surveys interannual to diurnal variations of tropical deep convective clouds and convective overshooting using the Advanced Microwave Sounding Unit B (AMSU-B) aboard the NOAA polar orbiting satellites from 1999 to 2005. The methodology used to detect tropical deep convective clouds is based on the advantage of microwave radiances to penetrate clouds. The major concentrations of tropical deep convective clouds are found over the intertropical convergence zone (ITCZ), the South Pacific convergence zone (SPCZ), tropical Africa, the Indian Ocean, the Indonesia maritime region, and tropical and South America. The geographical distributions are consistent with previous results from infrared-based measurements, but the cloud fractions present in this study are lower. Land–ocean and Northern–Southern Hemisphere (NH–SH) contrasts are found for tropical deep convective clouds. The mean tropical deep convective clouds have a slightly decreasing trend with −0.016% decade−1 in 1999−2005 while the mean convective overshooting has a distinct decreasing trend with −0.142% decade−1. The trends vary with the underlying surface (ocean or land) and with latitude. A secondary ITCZ occurring over the eastern Pacific between 2° and 8°S and only in boreal spring is predominantly found to be associated with cold sea surface temperatures in La Niña years. The seasonal cycles of deep convective cloud and convective overshooting are stronger over land than over ocean. The seasonal migration is pronounced and moves south with the sun from summer to winter and is particularly dramatic over land. The diurnal cycles of deep convective clouds and convective overshooting peak in the early evening and have their minima in the late morning over the tropical land. Over the tropical ocean the diurnal cycles peak in the morning and have their minima in the afternoon to early evening. The diurnal cycles over the NH and SH subtropical regions vary with the seasons. The local times of the maximum and minimum fractions also vary with the seasons. As the detected deep convective cloud fractions are sensitive to the algorithms and satellite sensors used and are influenced by the life cycles of deep convective clouds, the results presented in this study provide information complementary to present tropical deep convective cloud climatologies.

scholarly journals A simplified method for the detection of convection using high-resolution imagery from GOES-16

2021 ◽  
Vol 14 (5) ◽  
pp. 3755-3771
Author(s):  
Yoonjin Lee ◽  
Christian D. Kummerow ◽  
Milija Zupanski
Keyword(s):  
High Resolution ◽  
Rapid Development ◽  
Convective Cloud ◽  
Radar Data ◽  
High Temporal Resolution ◽  
Latent Heating ◽  
Infrared Sensors ◽  
Convective Clouds ◽  
Brightness Temperatures ◽  
Cloud Tops

Abstract. The ability to detect convective regions and to add latent heating to drive convection is one of the most important additions to short-term forecast models such as National Oceanic and Atmospheric Administration's (NOAA's) High-Resolution Rapid Refresh (HRRR) model. Since radars are most directly related to precipitation and are available in high temporal resolution, their data are often used for both detecting convection and estimating latent heating. However, radar data are limited to land areas, largely in developed nations, and early convection is not detectable from radars until drops become large enough to produce significant echoes. Visible and infrared sensors on a geostationary satellite can provide data that are more sensitive to small droplets, but they also have shortcomings: their information is almost exclusively from the cloud top. Relatively new geostationary satellites, Geostationary Operational Environmental Satellite-16 and Satellite-17 (GOES-16 and GOES-17), along with Himawari-8, can make up for this lack of vertical information through the use of very high spatial and temporal resolutions, allowing better observation of bubbling features on convective cloud tops. This study develops two algorithms to detect convection at vertically growing clouds and mature convective clouds using 1 min GOES-16 Advanced Baseline Imager (ABI) data. Two case studies are used to explain the two methods, followed by results applied to 1 month of data over the contiguous United States. Vertically growing clouds in early stages are detected using decreases in brightness temperatures over 10 min. For mature convective clouds which no longer show much of a decrease in brightness temperature, the lumpy texture from rapid development can be observed using 1 min high spatial resolution reflectance data. The detection skills of the two methods are validated against Multi-Radar/Multi-Sensor System (MRMS), a ground-based radar product. With the contingency table, results applying both methods to 1-month data show a relatively low false alarm rate of 14.4 % but missed 54.7 % of convective clouds detected by the radar product. These convective clouds were missed largely due to less lumpy texture, which is mostly caused by optically thick cloud shields above.

scholarly journals Impacts of Varying Concentrations of Cloud Condensation Nuclei On Deep Convective Cloud Updrafts – A Multimodel Assessment

2021 ◽  
Author(s):  
Peter J. Marinescu ◽  
Susan C. van den Heever ◽  
Max Heikenfeld ◽  
Andrew I. Barrett ◽  
Christian Barthlott ◽  
...  
Keyword(s):  
Cloud Condensation Nuclei ◽  
Convective Cloud ◽  
Ground Level ◽  
Condensation Nuclei ◽  
Thermal Buoyancy ◽  
Convective Clouds ◽  
Intercomparison Project ◽  
The Mean ◽  
Perturbation Pressure ◽  
Deep Convective Cloud

AbstractThis study presents results from a model intercomparison project, focusing on the range of responses in deep convective cloud updrafts to varying cloud condensation nuclei (CCN) concentrations amongst seven, state-of-the-art, cloud-resolving models. Simulations of scattered convective clouds near Houston, Texas are conducted, after being initialized with both relatively low and high CCN concentrations. Deep convective updrafts are identified, and trends in the updraft intensity and frequency are assessed. The factors contributing to the vertical velocity tendencies are examined to identify the physical processes associated with the CCN-induced, updraft changes.The models show several consistent trends. In general, the changes between the High-CCN and Low-CCN simulations in updraft magnitudes throughout the depth of the troposphere are within 15% for all of the models. All models produce stronger (~+5-15%) mean updrafts from ~4–7 km above ground level (AGL) in the High-CCN simulations, followed by a waning response up to ~8 km AGL in most of the models. Thermal buoyancy was more sensitive than condensate loading to varying CCN concentrations in most of the models and more impactful in the mean updraft responses. However, there are also differences between the models. The change in the amount of deep convective updrafts varies significantly. Furthermore, approximately half the models demonstrate neutral-to-weaker (~-5-0%) updrafts above ~8 km AGL, while the other models show stronger (~+10%) updrafts in the High-CCN simulations. The combination of the CCN-induced impacts on the buoyancy and vertical perturbation pressure gradient terms better explains these middle- and upper-tropospheric updraft trends than the buoyancy terms alone.

scholarly journals The time-space exchangeability of satellite retrieved relations between cloud top temperature and particle effective radius

2005 ◽  
Vol 5 (6) ◽  
pp. 11911-11928 ◽  
Author(s):  
I. M. Lensky ◽  
D. Rosenfeld
Keyword(s):  
Southern Africa ◽  
Convective Cloud ◽  
Effective Radius ◽  
Cloud Base ◽  
Convective Clouds ◽  
Rapid Scan ◽  
Fundamental Causes ◽  
Time Space ◽  
Cloud Tops ◽  
Cloud Top Temperature

Abstract. A 3-min 3-km rapid scan of the METEOSAT Second Generation geostationary satellite over southern Africa was applied to tracking the evolution of cloud top temperature (T) and particle effective radius (re) of convective elements. The evolution of T-re relations showed little dependence on time, leaving re to depend almost exclusively on T. Furthermore, cloud elements that fully grew to large cumulonimbus stature had the same T-re relations as other clouds in the same area with limited development that decayed without ever becoming a cumulonimbus. Therefore, a snap shot of T-re relations over a cloud field provides the same relations as composed from tracking the time evolution of T and re of individual clouds, and then compositing them. This is the essence of exchangeability of time and space scales, i.e., ergodicity, of the T-re relations for convective clouds. This property has allowed inference of the microphysical evolution of convective clouds with a snap shot from a polar orbiter. The fundamental causes for the ergodicity are suggested to be the observed stability of re for a given height above cloud base in a convective cloud, and the constant renewal of growing cloud tops with cloud bubbles that replace the cloud tops with fresh cloud matter from below.

scholarly journals The time-space exchangeability of satellite retrieved relations between cloud top temperature and particle effective radius

2006 ◽  
Vol 6 (10) ◽  
pp. 2887-2894 ◽  
Author(s):  
I. M. Lensky ◽  
D. Rosenfeld
Keyword(s):  
Southern Africa ◽  
Convective Cloud ◽  
Effective Radius ◽  
Cloud Base ◽  
Convective Clouds ◽  
Rapid Scan ◽  
Fundamental Causes ◽  
Time Space ◽  
Cloud Tops ◽  
Cloud Top Temperature

Abstract. A 3-minute 3-km rapid scan of the METEOSAT Second Generation geostationary satellite over southern Africa was applied to tracking the evolution of cloud top temperature (T) and particle effective radius (re) of convective elements. The evolution of T-re relations showed little dependence on time, leaving re to depend almost exclusively on T. Furthermore, cloud elements that fully grew to large cumulonimbus stature had the same T-re relations as other clouds in the same area with limited development that decayed without ever becoming a cumulonimbus. Therefore, a snap shot of T-re relations over a cloud field provides the same relations as composed from tracking the time evolution of T and re of individual clouds, and then compositing them. This is the essence of exchangeability of time and space scales, i.e., ergodicity, of the T-re relations for convective clouds. This property has allowed inference of the microphysical evolution of convective clouds with a snap shot from a polar orbiter. The fundamental causes for the ergodicity are suggested to be the observed stability of re for a given height above cloud base in a convective cloud, and the constant renewal of growing cloud tops with cloud bubbles that replace the cloud tops with fresh cloud matter from below.

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