Naresh Kumar

Winter frequency of western disturbances and precipitation indices over Himachal Pradesh, India: 1977-2007

The Himalayas have an important role in Indian weather and climate, since they control the western disturbances (WDs) during winter and the southwest monsoon during summer. During the winter months (December to March), westerly winds associated with WDs cause precipitation, sometimes along with heavy snowfall, extensive avalanches, etc., over Himachal Pradesh. Therefore, this study examined the temporal variability in the winter months frequency of WDs and various precipitation indices like wet days, rainy days, rather heavy and heavy precipitation days, and precipitation intensity during 1977 to 2007 over Himachal Pradesh. The study also examined synoptic features associated with intense WDs that caused heavy precipitation over the region during the same period. Analysis of data reveals a statistically significant (confidence level > 95%) decreasing trend in the frequency of WDs over this region. Since winter precipitation in Himachal Pradesh mainly occurs due to WDs, total winter precipitation and frequency of rather heavy and heavy precipitation days have decreased over the region. The analysis also shows a decrease of about 25% in heavy precipitation days and of 13% in total winter precipitation from their respective mean (from 1977 to 2007) over Himachal Pradesh.

Characteristics of Very Severe Cyclonic Storm “NARGIS” over the Bay of Bengal During 27 April to 3 May 2008

A very severe cyclonic storm crossed southwest coast of Myanmar near latitude 16.0°N between 1200 and 1400 UTC of 2 May 2008. It caused loss of more than 22,000 human lives in Myanmar. The special features of “Nargis” are given below. (i) The system continued to intensify even after the recurvature. (ii) The system moved almost in the easterly direction from 0600 UTC of 1 May till 1500 UTC of 2 May. (iii) The system maintained the intensity of very severe cyclonic storm for about 12 h after the landfall. (iv) It was the most devastating cyclone over the Bay of Bengal after the 1991 Bangladesh cyclone in term of loss of life and property.

Historical temporal variation in precipitation over Western Himalayan Region: 1857-2006

This study has examined the temporal variation in monthly, seasonal & annual precipitation over the Western Himalayan Region (WHR) and the influence of global teleconnections, like the North Atlantic Oscillation (NAO) and Southern Oscillation (SO) Indices on seasonal & annual precipitation. The Mann–Kendall non-parametric test is applied for trend detection and the Pettitt–Mann–Whitney test is used to detect possible shift. Maximum entropy spectral analysis is applied to find the periodicity in annual & seasonal precipitation. The study shows a non-significant decreasing trend in annual precipitation over WHR for the period 1857-2006. However, in seasonal precipitation, a significant decreasing trend is observed in monsoon and a significant increasing trend in post-monsoon season during the same period. The significant decrease in monsoon precipitation may be due to weakening of its teleconnection with NAO as well as SO Indices mainly during last three decades. It is observed that the probable change of year in annual & monsoon precipitation over WHR is 1979. The study also shows significant periodicities of 2.3-2.9 years and of 3.9-4.7 years in annual & seasonal precipitation over WHR.

Changes in Rainfall Concentration over India During 1871–2011

Change in rainfall pattern and its impact on the water resources is one of the important climatic problem. There are many studies in the literature that indicate about the change in rainfall pattern globally (De Luis et al. 2000; Hulme et al. 1998; Rodriguez-Puebla et al. 1998). Many studies carried out in India also showed variability in the rainfall on different temporal and spatial scales (Kripalani et al. 2003; Sahai et al. 2003). In India, rainfall is highly variable from place to place. Some regions like Western Ghats as well as Sub-Himalayan areas in North East and Meghalaya receive annual rainfall more than 200 cm while northern part of Kashmir, West Rajasthan and Punjab receive annual rainfall less than 50 cm.

Characteristics of Very Severe Cyclonic Storm “SIDR” over the Bay of Bengal During 11-16 November 2007

The year 2007 showed increased cyclonic activity over the Bay of Bengal, compared to recent years with the formation of nine cyclonic disturbances. Out of these disturbances, two cyclonic storms, including a very severe cyclonic storm “SIDR”, formed over the Bay of Bengal. This system crossed Bangladesh coast around 1700 UTC of 15 November 2007. The system caused heavy to very heavy rainfall over Bangladesh and northeastern states of India. According to media report, the wind speed of about 200 km/h prevailed over Bangladesh coast at the time of landfall and tidal wave of about 6 m inundated low lying areas of Bangladesh. It caused a loss of about 3,400 human lives and huge loss of property. The special features of “SIDR” are as follows. It was the first ever very severe cyclonic storm crossing Bangladesh after 1991 and first severe cyclonic storm after 1998 (Table 1). The system moved in a near northerly direction till a few hours before landfall and recurved northeastwards during landfall. It moved faster during 12 h before landfall. The size of the storm was less, though it had severe damage potential. The very severe cyclonic storm was monitored by the latest technological tools like Doppler Weather Radar (DWR), Automatic Weather Stations (AWS), and satellite derived products including atmospheric motion vectors (AMV).

The First Ever Super Cyclonic Storm “GONU” over the Arabian Sea During 1-7 June 2007: A Case Study

Four cyclonic storms including a super cyclonic storm (Gonu) formed over the north Indian Ocean during 2007. The first ever super cyclonic storm Gonu developed over the Arabian Sea as per the history recorded by IMD since 1877. It made its first landfall over Oman as a very severe cyclonic storm, and then emerged into the Gulf of Oman and made a second landfall over Iran as a cyclonic storm. Heavy to very heavy rainfall occurred over the eastern coast of Oman, causing flood and heavy damage. Gale winds with a speed of 100 km/h were recorded at Muscat at the time of landfall. About 50 persons died and estimated damage to property was about

BENZOTHIAZOLES AND AZA-ANALOGUES THEREOF USE AS ANTIBACTERIAL AGENTS

4.2 billion in Oman. The number of human deaths was 28 and loss of property was

Decline in horizontal surface visibility over India (1961–2008) and its association with meteorological variables

215 million over Iran. The special features of “Gonu” are as follows. It was the first ever super cyclonic storm developed over the Arabian Sea as per recorded history of IMD (1979, 1996, 2008) The super cyclonic storm, GONU made two landfalls over Oman and Iran. This was the second landfalling cyclonic storm over Iran after 4 June 1898 (IMD 1979, 2008).