scholarly journals A daytime climatological distribution of high opaque ice cloud classes over the Indian summer monsoon region observed from 25-year AVHRR data

2009 ◽  
Vol 9 (12) ◽  
pp. 4185-4196 ◽  
Author(s):  
A. Devasthale ◽  
H. Grassl
Keyword(s):  
Summer Monsoon ◽  
Indian Subcontinent ◽  
Deep Convection ◽  
Temporal Distribution ◽  
Radiative Balance ◽  
Ice Cloud ◽  
Brightness Temperatures ◽  
Spatio Temporal ◽  
Very High ◽  
Summer Monsoon Region

Abstract. A daytime climatological spatio-temporal distribution of high opaque ice cloud (HOIC) classes over the Indian subcontinent (0–40° N, 60° E–100° E) is presented using 25-year data from the Advanced Very High Resolution Radiometers (AVHRRs) for the summer monsoon months. The HOICs are important for regional radiative balance, precipitation and troposphere-stratosphere exchange. In this study, HOICs are sub-divided into three classes based on their cloud top brightness temperatures (BT). Class I represents very deep convection (BT<220 K). Class II represents deep convection (220 K

scholarly journals A daytime climatological distribution of high opaque ice cloud classes over the Indian summer monsoon region observed from 25-year AVHRR data

2009 ◽  
Vol 9 (1) ◽  
pp. 23-58 ◽  
Author(s):  
A. Devasthale ◽  
H. Grassl
Keyword(s):  
Summer Monsoon ◽  
Indian Subcontinent ◽  
Deep Convection ◽  
Class Ii ◽  
The Other ◽  
Class I ◽  
Western Coast ◽  
Convective Activity ◽  
Radiative Balance ◽  
Ice Cloud

Abstract. A daytime climatological spatio-temporal distribution of high opaque ice cloud (HOIC) classes over the Indian subcontinent (0–40° N, 60° E–100° E) is presented using 25-year data from the Advanced Very High Resolution Radiometers (AVHRRs) for the summer monsoon months. The HOICs are important for regional radiative balance, precipitation and troposphere-stratosphere exchange. In this study, HOICs are sub-divided into three classes based on their cloud top brightness temperatures (BT). Class I represents very deep convection (BT<220 K). Class II represents deep convection (220 K≤BT<233 K) and Class III background convection (233 K≤BT<253 K). Apart from presenting finest spatial resolution (0.1×0.1 degrees) and long-term climatology of such cloud classes from AVHRRs to date, this study for the first time illustrates on 1) how these three cloud classes are climatologically distributed during monsoon months, and 2) how their distribution changes during active and break monsoon conditions. It is also investigated that how many overshooting convective clouds reach the tropopause layer during individual monsoon months. It is seen that Class I and Class II clouds dominate the Indian subcontinent during monsoon. The movement of monsoon over continent is very well reflected in these cloud classes. During monsoon breaks strong suppression of convective activity is observed over the Arabian Sea and the western coast of India. On the other hand, the presence of such convective activity is crucial for active monsoon conditions and all-India rainfall. It is found that a significant fraction of HOICs (3–5%) reach the tropopause layer over the Bay of Bengal during June and over the north and northeast India during July and August. Many cases are observed when clouds penetrate the tropopause layer and reach the lower stratosphere. Such cases mostly occur during June compared to the other months.

scholarly journals Annual cycle of water vapour in the lower stratosphere over the Indian Peninsula derived from Cryogenic Frost-point Hygrometer observations

2018 ◽  
Author(s):  
Maria Emmanuel ◽  
Sukumarapillai V. Sunilkumar ◽  
Muhsin Muhammed ◽  
Buduru Suneel Kumar ◽  
Nagendra Neerudu ◽  
...  
Keyword(s):  
Water Vapour ◽  
Summer Monsoon ◽  
Lower Stratosphere ◽  
Indian Subcontinent ◽  
Monsoon Season ◽  
Deep Convection ◽  
Equatorial Station ◽  
Post Monsoon ◽  
Frost Point ◽  
Stratospheric Water Vapour

Abstract. In situ measurements of lower stratospheric water vapour employing Cryogenic Frost point Hygrometer (CFH) over two tropical stations, Trivandrum (8.53 °N, 76.87 °E) and Hyderabad (17.47 °N, 78.58 °E) over the Indian subcontinent are conducted as part of Tropical Tropopause Dynamics (TTD) monthly campaigns under GARNETS program. The annual variation of lower stratosphere (LS) water vapour clearly depicts the so called tape recorder effect at both the stations. The ascent rate of water vapour compares well with the velocity of Brewer-Dobson circulation and is slightly higher over the equatorial station when compared to the off-equatorial station. The column integrated water vapour in the LS varies in the range 1.5 to 4 g/m2 with low values during winter and high values during summer monsoon and post monsoon seasons and its variability shows the signatures of local dynamics. The variation in water vapour mixing ratio (WVMR) at the cold point tropopause (CPT) exactly follows the variation in CPT temperature. The difference in WVMR between the stations shows a semi-annual variability in the altitude region 18–20 km region with high values of WVMR during summer monsoon and winter over Hyderabad and during pre-monsoon and post-monsoon over Trivandrum. This difference is related to the influence of the variations in local CPT temperature and deep convection. The monsoon dynamics has a significant role in stratospheric water vapour distribution in summer monsoon season.

scholarly journals The Asian Summer Monsoon: Teleconnections and Forcing Mechanisms—A Review from Chinese Speleothem δ18O Records

Quaternary ◽  
2019 ◽  
Vol 2 (3) ◽  
pp. 26 ◽  
Author(s):  
Zhang ◽  
Brahim ◽  
Li ◽  
Zhao ◽  
Kathayat ◽  
...  
Keyword(s):  
Summer Monsoon ◽  
Asian Summer Monsoon ◽  
Temporal Distribution ◽  
The Holocene ◽  
North Atlantic Climate ◽  
Asian Summer ◽  
Spatio Temporal ◽  
Forcing Mechanisms ◽  
The Last Two Millennia ◽  
Global Population

Asian summer monsoon (ASM) variability significantly affects hydro-climate, and thus socio-economics, in the East Asian region, where nearly one-third of the global population resides. Over the last two decades, speleothem δ18O records from China have been utilized to reconstruct ASM variability and its underlying forcing mechanisms on orbital to seasonal timescales. Here, we use the Speleothem Isotopes Synthesis and Analysis database (SISAL_v1) to present an overview of hydro-climate variability related to the ASM during three periods: the late Pleistocene, the Holocene, and the last two millennia. We highlight the possible global teleconnections and forcing mechanisms of the ASM on different timescales. The longest composite stalagmite δ18O record over the past 640 kyr BP from the region demonstrates that ASM variability on orbital timescales is dominated by the 23 kyr precessional cycles, which are in phase with Northern Hemisphere summer insolation (NHSI). During the last glacial, millennial changes in the intensity of the ASM appear to be controlled by North Atlantic climate and oceanic feedbacks. During the Holocene, changes in ASM intensity were primarily controlled by NHSI. However, the spatio-temporal distribution of monsoon rain belts may vary with changes in ASM intensity on decadal to millennial timescales.

Quantitative study of atmospheric rivers in the Indian subcontinent

2021 ◽  
Author(s):  
Rosa V. Lyngwa ◽  
Munir Ahmad Nayak
Keyword(s):  
Water Vapor ◽  
Indian Subcontinent ◽  
Temporal Distribution ◽  
Large Degree ◽  
Water Vapor Transport ◽  
Boreal Summer ◽  
Atmospheric Rivers ◽  
Wind Speeds ◽  
Minimum Requirements ◽  
Spatio Temporal

&lt;p&gt;The principal sources of freshwater in India include precipitation, glaciers, and snowmelt. The former dominates the country&amp;#8217;s annual river water contribution, which is important for agriculture and livelihood of the residents, and the latter two sources contribute at a much lower fraction in comparison to precipitation to even meet the minimum requirements. However, there is a large degree of variations in their spatio-temporal distribution throughout the country. India receives a major portion of its annual precipitation during the boreal summer (June &amp;#8211; September). The well-known but relatively unexplored contributors to precipitation in India are atmospheric rivers (ARs). This study aims to understand the main climatological and dynamical differences between the Indian summer monsoon (ISM) and ARs in boreal summer. Zonal (&amp;#8216;u&amp;#8217;) and meridional (&amp;#8216;v&amp;#8217;) wind speeds, integrated water vapor transport (IVT), and integrated water vapor (IWV) are used to identify distinct features in ARs in the Indian sub-continent that can be used to distinguish them from ISM. The major differences between the two synoptic features were found in the increased zonal wind speed and moisture inputs during AR events, which often result in extreme precipitation and floods. Besides understanding them, the identification of ARs in this region and accounting for their existential contribution to moisture during peak rainfall seasons is critical for further hydrological impacts studies.&lt;/p&gt;

scholarly journals Spatio-Temporal Clustering of Sarawak Malaysia Total Protected Area Visitors

2021 ◽  
Vol 13 (21) ◽  
pp. 11618
Author(s):  
Abang Zainoren Abang Abdurahman ◽  
Syerina Azlin Md Nasir ◽  
Wan Fairos Wan Yaacob ◽  
Serah Jaya ◽  
Suhaili Mokhtar
Keyword(s):  
National Parks ◽  
Temporal Distribution ◽  
Temporal Analysis ◽  
Minimum Variance ◽  
Additional Information ◽  
Spatial And Temporal Analysis ◽  
Spatio Temporal ◽  
Underlying Trend ◽  
Very High ◽  
Minimum Variance Method

Based on data of visitors to national parks, nature reserves and wildlife sanctuaries in Sarawak, this study’s objective is to use the spatial and temporal analysis to describe the underlying trend and temporal pattern of local and foreign visitors and ultimately infer the temporal distribution of visitors to 18 different TPAs. The second aim of the study is to cluster the visitors according to the location of TPAs using Wards hierarchical clustering method. By comparing average monthly visitors’ count, we observed that the average number of monthly visitors significantly reflects the distribution concentration of visitors based on the spatial map. Findings indicate that the monthly distributions of local and foreign visitors differ according to different TPAs. The spatial and temporal analysis found that local visitors’ arrival is high at the end of the year while foreign visitors showed significant arrival during the months of July, August and September. The Wards minimum variance method was able to cluster TPAs local and foreign visitors into very high, high, medium and low visitor area. This study provides additional information that could contribute to identifying the periods of highest visitor pressure, design measures to manage the concentration of visitors and improve the overall visitors’ experience. The findings of the study are also important to respective local authorities in providing information for planning and monitoring tourism in TPAs. Consecutively, this will ensure sustainability of TPAs resources while protecting their biodiversity.

scholarly journals A climatological perspective of deep convection penetrating the TTL during the Indian summer monsoon from the AVHRR and MODIS instruments

2010 ◽  
Vol 10 (2) ◽  
pp. 2809-2834 ◽  
Author(s):  
A. Devasthale ◽  
S. Fueglistaler
Keyword(s):  
Tibetan Plateau ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Bay Of Bengal ◽  
Deep Convection ◽  
Radiative Heating ◽  
The Tibetan Plateau ◽  
Brightness Temperatures ◽  
Avhrr Data ◽  
The Impact

Abstract. The impact of very deep convection on the water budget and thermal structure of the tropical tropopause layer is still not well quantified, not least because of limitations imposed by the available observation techniques. Here, we present detailed analysis of the climatology of the cloud top brightness temperatures as indicators of deep convection during the Indian summer monsoon, and the variations therein due to active and break periods. We make use of the recently newly processed data from the Advanced Very High Resolution Radiometer (AVHRR) at a nominal spatial resolution of 4 km. Using temperature thresholds from the Atmospheric Infrared Sounder (AIRS), the AVHRR brightness temperatures are converted to climatological mean (2003–2008) maps of cloud amounts at 200, 150 and 100 hPa. Further, we relate the brightness temperatures to the level of zero radiative heating, which may allow a coarse identification of convective detrainment that will subsequently ascend into the stratosphere. The AVHRR data for the period 1982–2006 are used to document the differences in deep convection between active and break conditions of the monsoon. The analysis of AVHRR data is complemented with cloud top pressure and optical depth statistics (for the period 2003–2008) from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua satellite. Generally, the two sensors provide a very similar description of deep convective clouds. Our analysis shows that most of the deep convection occurs over the Bay of Bengal and Central Northeast India. Very deep convection over the Tibetan plateau is comparatively weak, and may play only a secondary role in troposphere-to-stratosphere transport. The deep convection over the Indian monsoon region is most frequent in July/August, but the very highest convection (coldest tops, penetrating well into the TTL) occurs in May/June. Large variability in convection reaching the TTL is due to monsoon break/active periods. During the monsoon break period, deep convection reaching the TTL is almost entirely absent in the western part of the study area (i.e. 60°–75° E), while the distribution over the Bay of Bengal and the Tibetan Plateau is less affected. Although the active conditions occur less frequently than the break conditions, they may have a larger bearing on the composition of the TTL within the monsoonal anticyclone, and tracer transport into the stratosphere because of deep convection occurring over anthropogenically more polluted regions.

scholarly journals The vertical structure of cloud radiative heating over the Indian subcontinent during summer monsoon

2015 ◽  
Vol 15 (20) ◽  
pp. 11557-11570 ◽  
Author(s):  
E. Johansson ◽  
A. Devasthale ◽  
T. L'Ecuyer ◽  
A. M. L. Ekman ◽  
M. Tjernström
Keyword(s):  
Summer Monsoon ◽  
Vertical Structure ◽  
Indian Subcontinent ◽  
Deep Convection ◽  
Radiative Heating ◽  
Upper Troposphere ◽  
Tropical Tropopause ◽  
Radiative Impact ◽  
Stratiform Clouds ◽  
Cooling Effects

Abstract. Clouds forming during the summer monsoon over the Indian subcontinent affect its evolution through their radiative impact as well as the release of latent heat. While the latter is previously studied to some extent, comparatively little is known about the radiative impact of different cloud types and the vertical structure of their radiative heating/cooling effects. Therefore, the main aim of this study is to partly fill this knowledge gap by investigating and documenting the vertical distributions of the different cloud types associated with the Indian monsoon and their radiative heating/cooling using the active radar and lidar sensors onboard CloudSat and CALIPSO. The intraseasonal evolution of clouds from May to October is also investigated to understand pre-to-post monsoon transitioning of their radiative heating/cooling effects. The vertical structure of cloud radiative heating (CRH) follows the northward migration and retreat of the monsoon from May to October. Throughout this time period, stratiform clouds radiatively warm the middle troposphere and cool the upper troposphere by more than ±0.2 K day−1 (after weighing by cloud fraction), with the largest impacts observed in June, July and August. During these months, the fraction of high thin cloud remains high in the tropical tropopause layer (TTL). Deep convective towers cause considerable radiative warming in the middle and upper troposphere, but strongly cool the base and inside of the TTL. This cooling is stronger during active (−1.23 K day−1) monsoon periods compared to break periods (−0.36 K day−1). The contrasting radiative warming effect of high clouds in the TTL is twice as large during active periods than in break periods. These results highlight the increasing importance of CRH with altitude, especially in the TTL. Stratiform (made up of alto- and nimbostratus clouds) and deep convection clouds radiatively cool the surface by approximately −100 and −400 W m−2 respectively while warming the atmosphere radiatively by about 40 to 150 W m−2. While the cooling at the surface induced by deep convection and stratiform clouds is largest during active periods of monsoon, the importance of stratiform clouds further increases during break periods. The contrasting CREs (cloud radiative effects) in the atmosphere and at surface, and during active and break periods, should have direct implications for the monsoonal circulation.

scholarly journals Spatio-Temporal Distribution of Deep Convection Observed along the Trans-Mexican Volcanic Belt

2021 ◽  
Vol 13 (6) ◽  
pp. 1215
Author(s):  
José Francisco León-Cruz ◽  
Cintia Carbajal Henken ◽  
Noel Carbajal ◽  
Jürgen Fischer
Keyword(s):  
Extreme Precipitation ◽  
Deep Convection ◽  
Temporal Distribution ◽  
Volcanic Belt ◽  
Convective Cloud ◽  
Extreme Precipitation Events ◽  
Mexican Volcanic Belt ◽  
Spatio Temporal ◽  
Terrain Features ◽  
Precipitation Events

Complex terrain features—in particular, environmental conditions, high population density and potential socio-economic damage—make the Trans-Mexican Volcanic Belt (TMVB) of particular interest regarding the study of deep convection and related severe weather. In this research, 10 years of Moderate-Resolution Imaging Spectroradiometer (MODIS) cloud observations are combined with Climate Hazards Group Infrared Precipitation with Station (CHIRPS) rainfall data to characterize the spatio-temporal distribution of deep convective clouds (DCCs) and their relationship to extreme precipitation. From monthly distributions, wet and dry phases are identified for cloud fraction, deep convective cloud frequency and convective precipitation. For both DCC and extreme precipitation events, the highest frequencies align just over the higher elevations of the TMVB. A clear relationship between DCCs and terrain features, indicating the important role of orography in the development of convective systems, is noticed. For three sub-regions, the observed distributions of deep convective cloud and extreme precipitation events are assessed in more detail. Each sub-region exhibits different local conditions, including terrain features, and are known to be influenced differently by emerging moisture fluxes from the Gulf of Mexico and the Pacific Ocean. The observed distinct spatio-temporal variabilities provide the first insights into the physical processes that control the convective development in the study area. A signal of the midsummer drought in Mexico (i.e., “canícula”) is recognized using MODIS monthly mean cloud observations.

scholarly journals A climatological perspective of deep convection penetrating the TTL during the Indian summer monsoon from the AVHRR and MODIS instruments

2010 ◽  
Vol 10 (10) ◽  
pp. 4573-4582 ◽  
Author(s):  
A. Devasthale ◽  
S. Fueglistaler
Keyword(s):  
Tibetan Plateau ◽  
Summer Monsoon ◽  
Indian Summer Monsoon ◽  
Bay Of Bengal ◽  
Deep Convection ◽  
Radiative Heating ◽  
The Tibetan Plateau ◽  
Brightness Temperatures ◽  
Avhrr Data ◽  
The Impact

Abstract. The impact of very deep convection on the water budget and thermal structure of the tropical tropopause layer is still not well quantified, not least because of limitations imposed by the available observation techniques. Here, we present detailed analysis of the climatology of the cloud top brightness temperatures as indicators of deep convection during the Indian summer monsoon, and the variations therein due to active and break periods. We make use of the recently newly processed data from the Advanced Very High Resolution Radiometer (AVHRR) at a nominal spatial resolution of 4 km. Using temperature thresholds from the Atmospheric Infrared Sounder (AIRS), the AVHRR brightness temperatures are converted to climatological mean (2003–2008) maps of cloud amounts at 200, 150 and 100 hPa. Further, we relate the brightness temperatures to the level of zero radiative heating, which may allow a coarse identification of convective detrainment that will subsequently ascend into the stratosphere. The AVHRR data for the period 1982–2006 are used to document the differences in deep convection between active and break conditions of the monsoon. The analysis of AVHRR data is complemented with cloud top pressure and optical depth statistics (for the period 2003–2008) from the Moderate Resolution Imaging Spectroradiometer (MODIS) onboard Aqua satellite. Generally, the two sensors provide a very similar description of deep convective clouds. Our analysis shows that most of the deep convection occurs over the Bay of Bengal and central northeast India. Very deep convection over the Tibetan plateau is comparatively weak, and may play only a secondary role in troposphere-to-stratosphere transport. The deep convection over the Indian monsoon region is most frequent in July/August, but the very highest convection (coldest tops, penetrating well into the TTL) occurs in May/June. Large variability in convection reaching the TTL is due to monsoon break/active periods. During the monsoon break period, deep convection reaching the TTL is almost entirely absent in the western part of the study area (i.e. 60 E–75 E), while the distribution over the Bay of Bengal and the Tibetan Plateau is less affected. Although the active conditions occur less frequently than the break conditions, they may have a larger bearing on the composition of the TTL within the monsoonal anticyclone, and tracer transport into the stratosphere because of deep convection occurring over anthropogenically more polluted regions.

scholarly journals Environmental factors modulating the bathymetric distribution of the demographic groups of Achelous spinimanus (Crustacea)

2019 ◽  
Vol 14 (1) ◽  
pp. 13-28 ◽  
Author(s):  
Camila H. Bernardo ◽  
Veronica Pereira Bernardes ◽  
Aline Nonato de Sousa ◽  
Gabriel Fellipe Barros Rodrigues ◽  
Thiago Elias da Silva ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Temporal Distribution ◽  
Southeastern Brazil ◽  
Adult Males ◽  
Bathymetric Distribution ◽  
Demographic Groups ◽  
Different Depths ◽  
Males And Females ◽  
Spatio Temporal ◽  
Very High

The spatio-temporal distribution of Achelous spinimanus demographic groups (juveniles, and adult males and females) and its relation with environmental factors was analyzed in the region of Ubatuba, southeastern Brazil. We performed the samplings from January to December 2000, at eight sites of different depths. A total of 402 specimens of A. spinimanus was captured. The lowest abundance of all demographic groups occurred in summer, while in winter and spring the abundance of adults was very high. Spatially, juveniles were found at 5 to 35m of depth, while adults at 15 to 40m, but were more abundant at 25m. The low abundance of all demographic groups during summer is probably due to the arrival of the South Atlantic Central Water in the region, which decreased the water temperature and salinity. These changes caused the migration of A. spinimanus to more sheltered places of the bay, possibly due to more favorable environmental conditions. The high abundance of the demographic groups at 25m of depth was due to its more heterogeneous sediment, and to avoid competition with other species more abundant in shallower areas. Therefore, the factors that modulate the distribution of A. spinimanus may differ depending on the ontogenetic phase.

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