Hamza Varikoden

Hamza Varikoden
Indian Institute of Tropical Meteorology | IITM · Centre for Climate Change Research

About

80
Publications
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866
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Additional affiliations
June 2009 - present
Indian Institute of Tropical Meteorology
Position
  • Researcher

Publications

Publications (80)
Preprint
In this study, we investigated the possible relation between the Indian summer monsoon and the combination of the different phases of Pacific Decadal Oscillation (PDO) and El Niño Southern Oscillation (ENSO) before and after the climate shift in 1976. This study is carried out using IMD’s rainfall dataset, HadISST v1.1 dataset and twentieth century...
Conference Paper
Full-text available
Indian summer monsoon provides rainfall over a large area during 01 June to 30 September and it plays vital role for the water needs of the population of India. It is intense because strong differential heating prevails over the region due to geographical features of India. Further, it can be viewed as a synoptic scale ocean-atmosphere interactive...
Article
Full-text available
Changes in rainfall patterns can have a profound impact on water availability, and therefore, examining the variability of rainfall is critical in addressing water resources and regional climate change. Tripura state of northeast India is known to have received a high amount of rainfall in the past few decades, but currently the region suffers from...
Article
An out‐of‐phase pattern of fishery between anchovy and sardine exists in upwelling systems of different geographical locations. We examined the inverse relationship of anchovy (Stolephorus sp., Engraulidae) and sardine (Sardinella longiceps, Clupeidae) fishery along the coast of the south‐eastern Arabian Sea (SEAS) by analysing the annual landing d...
Article
Full-text available
Structure of the atmospheric boundary layer (ABL) over the west coast of India has been investigated using conserved variable analysis (CVA). Daily radiosonde data of Thiruvananthapuram (TVM), Mangalore (MNG) and Mumbai (MUM) at 00 UTC during the monsoon season of 2018 procured from India Meteorological Department have been primarily utilised for t...
Article
Full-text available
In the present paper, the variabilities and long-term trends of summer monsoon rainfall for different intensity bins (dry, low, moderate, high, very high, and extreme) are studied for five homogeneous regions, namely Northeast India (NEI), Northcentral India (NCI), Northwest India (NWI), Westcentral India (WCI), and Peninsular India (PI) for 118 ye...
Article
We examine the projected changes in Indian summer monsoon rainfall (ISMR) and El Niño Southern Oscillation (ENSO) along with their changing relationships by the end of 21st century using Coupled Model Inter Comparison Project Phase5 (CMIP5) models. The historical (1951–2005) and future (2050–2099) projections of ISMR were assessed in addition to th...
Article
Full-text available
The present study explored the influence of different convective parameters such as lower tropospheric stability (LTS), low and medium cloud covers (LCC and MCC), and convective available potential energy (CAPE) on the regional variability of Indian summer monsoon rainfall (ISMR). The variabilities and trends of summer monsoon rainfall over the wes...
Article
We investigate the characteristics and causes of extreme rainfall event occurred in Kerala (south western regions of the peninsular India) in August 2018. The changes in large-scale circulations over the Indo-Pacific domain and their association with regional circulation features, which made the extreme rainfall in Kerala are analysed. During this...
Article
The study explores the spatial variability and related characteristics of south Asian summer monsoon rainfall and extreme rainfall events based on APHRODITE rainfall products. An attempt was also made to investigate their association with global climate indices. Most of the South Asian regions are vulnerable to extreme rainfall events and many of t...
Article
The study investigates thermodynamic structure of the atmospheric boundary layer (ABL) over the west coast of India during the southwest monsoon season. Radiosonde profiles at 00 UTC (0530 IST) are utilized for three stations, namely Thiruvananthapuram (TVM), Mangalore (MNG) and Mumbai (MUM) to represent south, central and north parts of the west c...
Article
Full-text available
The Indian summer monsoon rainfall (ISMR) during June to September contributes most of the annual rainfall over India and plays an important role in Indian agriculture and thus the economy. It exhibits high spatio-temporal variabilities forced from both internal and external factors, which are important for better understanding and prediction of IS...
Article
Full-text available
The sub-daily variability of latent (LHF) and sensible heat flux (SHF) in the Bay of Bengal (BoB) during the summer (May–September) is examined using moored buoys data at 8° N (2008 and 2011), 12° N (2010, 2011, 2012, 2013, 2014, and 2015), and 15° N (2009, 2013, 2014, and 2015) along 90° E. In the weak wind regime (< 6 ms⁻¹), LHF loss from the oce...
Article
Full-text available
Changes in rainfall affect drinking water, river and surface runoff, soil moisture, groundwater reserve, electricity generation, agriculture production and ultimately the economy of a country. Trends in rainfall, therefore, are important for examining the impact of climate change on water resources for its planning and management. Here, as analysed...
Article
The variability of West Pacific Subtropical High (WPSH) during the peak monsoon (July‐August) season for the period 1951‐2015 and its association with Indian summer monsoon rainfall (ISMR) is investigated based on various observational data sets. In the present study, we explored the long term variability of WPSH based on location index (zonal disp...
Article
Full-text available
This study explores the potential of atmospheric moisture content, its transport and its divergence over the ocean and land as proxies for the variability of Indian summer monsoon rainfall (ISMR) for the period 1950–2019. The analyses using multiple linear regression reveal that the interannual and intraseasonal variability of ISMR and the mean ISM...
Preprint
During 2015, the southwest monsoon (SWM) rainfall over the country remained deficient with seasonal rainfall of about 86% of the long period average (Table 1.1). Last year, the seasonal rainfall deficiency over the country as a whole was 12% (www.imd.gov.in). Thus, this is a fourth episode of two consecutive years, with deficient monsoon, similar t...
Article
Full-text available
The El Niño Southern Oscillation (ENSO) is an important coupled ocean–atmosphere phenomenon in the tropical Pacific and an important modulator of the spatio-temporal variability of Indian summer monsoon rainfall (ISMR). Here, we explore the impact of ENSO during onset (June), peak (July–August) and withdrawal (September) phases of ISMR for the peri...
Article
In this study, we explored the changes in the Indian Ocean Dipole‐Indian summer monsoon rainfall (IOD‐ISMR) relationship from early (1951–1980) to recent (1986–2015) multidecades during onset (June), peak (July–August) and withdrawal (September) phases of Indian summer monsoon. The analyses indicate that the IOD‐ISMR relationship is strengthening (...
Article
Atmospheric ammonia (NH3) is an alkaline gas and a prominent constituent of the nitrogen cycle that adversely affects ecosystems at higher concentrations. It is a pollutant, which influences all three spheres such as haze formation in the atmosphere, soil acidification in the lithosphere, and eutrophication in water bodies. Atmospheric NH3 reacts w...
Article
Varikoden, H.; Roja, C.; Revadekar, J.V., and Milind, M., 2020. Rainfall variation in major river basins in India and the association with the Indo-Pacific Oceans. In: Sheela Nair, L.; Prakash, T.N.; Padmalal, D., and Kumar Seelam, J. (eds.), Oceanic and Coastal Processes of the Indian Seas. Journal of Coastal Research, Special Issue No. 89, pp. 1-...
Article
Trends and features of Atmospheric Boundary Layer (ABL) over southern part of west coast of India has been studied using MERRA datasets for 1980–2018 during different seasons incorporating the marine and continental influences. A significant decrease in the ABL height (ABLH) has been observed in the westerly regimes of the west coast. The shallow A...
Article
Full-text available
A regional tree ring-width index chronology prepared from various tree core samples of the western Himalaya has been analyzed in relation to climate fluctuations. The correlation analysis of tree ring chronology shows significant positive correlations with regional rainfall and standardized precipitation evapotranspiration index (SPEI) and negative...
Article
This study examines the response of surface layer parameters and ABL height (ABLH) to the change in cloudiness over Kochi. Outgoing long wave radiation (OLR) is considered as a proxy for the cloudiness. Temperature, horizontal wind speed, vertical velocity variance (VVV), sensible heat flux, momentum flux, turbulent kinetic energy (TKE), drag coeff...
Article
Full-text available
We observe significant changes in the ENSO–Indian summer monsoon rainfall (ISMR) relationship in past three multidecadal epochs (early epoch: 1931–1960, middle epoch: 1961–1990, and recent epoch: 1991–2015) based on consistent correlation. The rainfall during early epoch was above normal, however, in other two epochs it was relatively dry. The ENSO...
Article
Full-text available
In the present study, seven-year-long observations of rain microphysical properties are presented using a ground-based disdrometer located at Braemore; a site on the windward slope of the Western Ghats (WG) over the Indian Peninsula. The annual cycle of rainfall shows a bimodal distribution with a primary peak during summer monsoon and secondary pe...
Article
Full-text available
The extreme rainfall events over India during 2017 southwest monsoon and associated mechanisms are investigated using daily rainfall, winds and SST data sets. Extreme events occurred over mainly four locations according to the designed criteria, which are westcentral India (WC), central India (CI), northeast (NE) India and northwest coastal region...
Article
Hydrological disasters are recurrent over northeast Indian region (NEI) due to heavy downpour within a short span of time. Therefore, we discuss characteristics of rainfall extremes during the southwest monsoon over NEI, their evolution and dissipation features using rainfall data from TRMM 3B42 V7 and CPC for 16 years from 2000 to 2015. Circulatio...
Article
Westward propagation and the dynamics of intensification of Lakshadweep low (LL) have been investigated in detail. In this study, it is observed that LL is not propagated westwards in a single stretch to the western boundary of the southern Arabian Sea but takes place in multiple phases of propagation as well as through multiple eddy formations. LL...
Article
Full-text available
This study presents the contrasting trends of rainfall in the northern and southern Western Ghats (WG) and examines possible reasons for the phenomenon. The WG is one of the important mountain ranges that run parallel to the west coast of India. The mountain chain lies almost perpendicular to the low level jet stream (LLJ) and hence, receives about...
Article
This study explores the features of atmospheric surface layer over Kochi during active and weak phases of the southwest monsoon season. The classification of active and weak phases of monsoon is made on the basis of monsoon organized convection over the region. When the monsoon organized convection is over (away from) Kochi, considered it as an act...
Article
An attempt has been made to classify stratiform and convective rain using an impact type disdrometer at a tropical coastal site based on (Testud et al., 2001) method. Using this classification scheme, all rain events were analysed and computed their duration (minutes) and accumulated water (mm) in convective, stratiform, transition and mixed rain t...
Article
Full-text available
India is home for more than a billion people and its economy is largely based on agrarian society. Therefore, rainfall received not only decides its livelihood, but also influences its water security and economy. This situation warrants continuous surveillance and analysis of Indian rainfall. These kinds of studies would also help forecasters to be...
Article
Full-text available
Soil moisture is a key parameter in the prediction of southwest monsoon rainfall, hydrological modelling, and many other environmental studies. The studies on relationship between the soil moisture and rainfall in the Indian subcontinent are very limited; hence, the present study focuses the association between rainfall and soil moisture during dif...
Article
This study undertakes a comprehensive assessment of dynamical downscaling of summer monsoon (June–September; JJAS) rainfall over heterogeneous regions namely the Western Ghats (WG), Central India (CI) and North-Eastern Region (NER) for long term mean, excess and deficit episodes for the historical period from 1951 to 2005. This downscaling assessme...
Article
The effect of global climate change on Indian summer monsoon has been analysed with special emphasis on active-break cycle. The changes in intensity and duration of active and break monsoon conditions towards the end of the century are studied by using 850 hPa zonal circulations. The analysis is carried out using twenty year climatology of historic...
Article
The Western Ghats (WG) of India are basically north-south oriented mountains having narrow zonal width with a steep rising western face. The summer monsoon winds during June to September passing over the Arabian Sea are obstructed by the WG and thus orographically uplift to produce moderate-to-heavy precipitation over the region. However, it is see...
Article
Full-text available
The eastern Pacific Ocean received a record highest number of sub-tropical convective activities during boreal summer (June–September) of 2015, since last four decades. The associated rainfall distribution was also atypical with anomalously enhanced rainfall extending from equator to sub-tropical central-eastern Pacific. The present analysis reveal...
Article
Full-text available
Drop size distribution (DSD) over the tropical region exhibit pronounced variations during different monsoon seasons. Measurements from an impact type Joss-Waldovgel disdrometer is used for characterization of DSD and its integral parameters over a tropical coastal station (Thiruvananthapuram, 8.310 N, 76.540 E, 20 m ASL). Rain events were identifi...
Article
The Sultanate of Oman is located in the south-eastern part of the Arabian Peninsula and covers the larger part of the southern coasts of the Arabian Peninsula in both arid and semi-arid environments except for the southern part which is swept by the monsoon affecting the Arabian Sea during the period from June to September. The summer rainfall over...
Article
The oceans and the atmosphere are tightly linked and they together form the most dynamic component of the climate system. Topography and proximity to the surrounding seas of the region determine the temperature of the area. West Coast (WC) of India is a high elevated region surrounded by large oceanic area, therefore, an attempt is made in this stu...
Article
Full-text available
The Indian summer (JJAS) shows high variability in both space and timescales. Changes in precipitation extremes play an important role on the regional scale due to their serious socio-economic consequences. This study, therefore, is mainly focused on understanding the variation of precipitation extremes during summer monsoon season in the presence...
Article
A detailed analysis of the precipitation pattern of the Arabian Peninsula and its temporal and spatial variability were investigated in connection with ENSO. Also, the variability of precipitable water and circulation characteristics was examined for a better understanding. The study was carried out utilizing TRMM rainfall, NOAA OLR, precipitable w...
Article
Full-text available
Rainfall is the major climatic factor that affects the growth and distribution of natural vegetation at a regional scale. The high space–time variability of rainfall in the Tunga and Bhadra river basins caused by the high-elevation Western Ghats mountains forces changes in the seasonal distribution of local vegetation. Understanding the relationshi...
Article
Full-text available
Onset features of the Summer monsoon-2007 were analyzed using data from five different sources, namely, the Tropical Rainfall Measuring Mission (TRMM) 3-hourly rainfall, National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) wind reanalysis data set, NOAA Outgoing Longwave Radiation (OLR), cloud imageries...
Article
Onset features of the Summer monsoon-2007 were analyzed using data from five different sources, namely, the Tropical Rainfall Measuring Mission (TRMM) 3-hourly rainfall, National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) wind reanalysis data set, NOAA Outgoing Longwave Radiation (OLR), cloud imageries...
Article
Understanding the conditions of droughts are imperative for many purposes especially in planning and agricultural fields. In this paper an attempt is made to analyse rainfall distribution during droughts associated with El Niño and non-El Niño events using India Meteorological Department (IMD) daily rainfall data set having a spatial resolution of...
Article
A better understanding of the factors responsible for the variability in Indian summer monsoon rainfall (ISMR) is important in the present day climate because it is vulnerable to climate change. Here, we report the relationship between the Atlantic and Pacific sea surface temperature (SST) anomalies with ISMR. We developed a new ISMR index based on...
Article
Full-text available
The Tropical Rainfall Measuring Mission (TRMM) rainfall product 3B42-V7 and the telemetric station data sets of years 2010 and 2011 for the monsoon season were used to study the spatial and temporal variability of the daily rainfall in Tunga and Bhadra River basins in Karnataka. The daily rain observations of gauge and TRMM estimates show correlati...
Article
Thunderstorms are of much importance in tropics, as this region is considered to have central role in the convective overturn of the atmosphere and play an important role in rainfall activity. It is well known that El Niño and La Niña are well associated with significant climate anomalies at many places around the globe. Therefore, an attempt is ma...
Article
Full-text available
The Tropical Rainfall Measuring Mission (TRMM) rainfall product 3B42-V7 and the telemetric station data sets of years 2010 and 2011 for the monsoon season were used to study the spatial and temporal variability of the daily rainfall in Tunga and Bhadra River basins in Karnataka. The daily rain observations of gauge and TRMM estimates show correlati...
Article
The present paper presents a diagnostic study of two recent monsoon years, of which one is dry monsoon year (2009) and the other is wet monsoon year (2010). The study utilized the IMD gridded rainfall data set in addition to the Reynolds SST, NCEP-NCAR reanalysis wind and temperature products, and NOAA OLR. The study revealed that the months July a...
Article
In general Indian summer monsoon rainfall did not show any significant trend in all Indian summer monsoon rainfall series, however, it was reported that the ISMR is subjected to spatial trends. This paper made an attempt to bring out long term trends of different intensity classes of summer monsoon rainfall in different regions of Indian subcontine...
Article
In general Indian summer monsoon rainfall did not show any significant trend in all Indian summer monsoon rainfall series, however, it was reported that the ISMR is subjected to spatial trends. This paper made an attempt to bring out long term trends of different intensity classes of summer monsoon rainfall in different regions of Indian subcontine...
Article
Regional characteristics of Indian Summer Monsoon Rainfall (ISMR) during dry and wet monsoon years associated with El Niño Southern Oscillation (ENSO) and non-ENSO (normal) periods are investigated. Four cases such as wet monsoon years associated with ENSO (EW) and non-ENSO (NW) events and dry monsoon years associated with ENSO (ED) and non-ENSO (N...
Article
Full-text available
Investigations were carried out on the data from Braemore mountain observatory (Lat.: 8°45’N, Long.: 77°5’E) using a single lens Ceilomter (LIDAR), an Electric Field Mill and a portable Automatic Weather Station throughout the year 2010. The simultaneous data collected from the above instruments indicate the existence of strong updrafts followed by...
Article
This paper deals with the diurnal and spatial variation of summer monsoon (JJAS) rainfall, extremes and its frequency for a period of 12 years using the TRMM (Tropical Rainfall Measuring Mission) rain rate data set. Rainfall and frequency of rain events are more observed over the western coastal belts, northeastern regions, foothills of Himalayas a...
Article
This paper discusses the abnormal changes in weather elements observed at a tropical mountain location and a coastal station in India. Abnormal changes were noticed in the atmospheric parameters at a time close to the occurrence of tsunami on the Indian coasts due to high magnitude earthquakes in the Sumatra region on 26 December 2004. Close to the...
Article
Full-text available
This study aims to investigate the characteristic features of cloud base height (CBH) over Thiruvananthapuram during different seasons. CBH data were used for the present work derived from the Vaisala Laser Ceilometer, CL31 (VLC) installed at the campus of the Centre for Earth Science Studies, Akkulam (8.29° N, 76.59° E, 15 m above sea level). The...
Article
Using the rain rate from Tropical Rainfall Measuring Mission (TRMM) 3 h data, we made an attempt to explore the diurnal variation of rainfall occurrences in the spatial domain of Peninsular Malaysia. This data set is available for 10 years period from 1999 to 2008 at a high spatial resolution of 25 km latitude-longitude grid. The rainfall character...
Article
The present study is focused on the intensity distribution of rainfall in different classes and their contribution to the total seasonal rainfall. In addition, we studied the spatial and diurnal variation of the rainfall in the study areas. For the present study, we retrieved data from TRMM (Tropical Rain Measuring Mission) rain rate available in e...
Article
A distinct cold tongue has recently been noticed in the South China Sea during the winter monsoon, with the cold tongue temperature minimum occurring in the January or February. This cold tongue shows significant links with the Maritime Continent’s rainfall during the winter period. The cold tongue and its interaction with the Maritime Continent’s...
Conference Paper
A Vaisala Laser Ceilometer which employs the LIDAR technique with a 910 nm laser diode for measurement of cloud base height, sky condition and vertical visibility was set up at a tropical coastal station Thiruvananthapuram (8.29° N, 76.59° E)at Kerala state, India. Measurements of cloud base height during different rain spells were made to understa...