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Efficiency of Severe Recorded Rainstorms over Maharashtra State

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Advances in Atmospheric Sciences 1995年第1期12卷 103-108页

作者： B.D.Kulkarni Miss Shobha Nandargi O. N. Dhar indian institute of tropical meteorology Pune -411 008 India Indian Institute of Tropical Meteorology Pune -411 008 India Indian Institute of Tropical Meteorology Pune -411 008 India

12 severe rainstorms have been experienced by different meteorological sub-divisions of Maharashtra State during the last 100-year period from 1891-1990. For each of the rainstorms efficiency factors (i.e. P/ M ratios) were worked out for maximum one-day duration and for three standard areas of 1000, 5000, and 10,000 km2. Comparison of these ratios with the past has shown that the most efficient rainstorm over Maharashtra was the rainstorm of June, 1908 over the Vidarbha region whose full DAD data as well as isohyetal pattern have been given.

关键词： Rainstonn Depth-area -duration (DAD) Efficiency factor of rainstorms Probable Maximum Precipitation (PMP)

Aerosol-cloud-precipitation interactions:A challenging problem in regional environment and climate research

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Particuology 2013年第1期11卷 25-33页

作者： P.C.S.Devara M.G.Manoj indian institute of tropical meteorology Pune 411 008Maharashtra.India

Aerosols affect clouds in two broad ways：（i） presence of more number of aerosols leads to formation of more smaller droplets, and reduces coalescence, resulting in brighter clouds that reflect more solar energy back to space, hence they contribute to cooling of the Earth＇s surface and （ii） numerous smaller cloud droplets tend to reduce precipitation and change the extent of cloud cover and increase cloud lifetime and albedo. One of our recent studies on aerosols over the lndo-Gangetic Plains （IGP） relative to the pristine oceans to the south of indian Ocean showed that highly absorbing aerosols could potentially lead to the revival of active condition preceded by long break. The absorption of solar radiation by aerosols such as black carbon and desert dust produces surface cooling and local stabilization of lower atmosphere. This stability effect is overcome by the enhanced moisture convergence due to the meridional gradient of aerosol-induced heating. In some other studies, we showed association between cloud thickness and cloud to sub-cloud ratio （SCR）, aerosol variability （in terms of aerosol optical depth and aerosol index） and monsoon precipitation and climate over regional scale. This paper provides an overview of some salient results that have been obtained from the studies conducted, using the ground- and space-based active and passive remote sensing techniques, at the indian institute of tropical meteorology （IITM）, pune, india in the recent decade.

关键词： AerosoLs Clouds Lidar Solar radiometry Radiation Satellites

RELATIONSHIP BETWEEN 500 hPa RIDGE AXIS POSITIONS OVER THE indian AND THE WEST PACIFIC REGIONS AND THE indian SUMMER MONSOON RAINFALL

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Advances in Atmospheric Sciences 1986年第3期3卷 349-359页

作者： S.V.Singh,S.R.Inamdar,R.H.Kripalani,K.D.Prasad indian institute of tropical meteorology pune-411 005 india indian institute of tropical meteorology pune-411 005 india indian institute of tropical meteorology pune-411 005 india indian institute of tropical meteorology pune-411 005 india

500 hPa ridge positions over the indian and the West Pacific regions during April are related with the summer monsoon rainfall over india. The ridge position over the indian region shows better relation with monsoon rainfall than that shown by the ridge over the Pacific region. The multiple correlation of these ridge positions with monsoon rainfall exceeds 0.7. These predictive relationships are better than those shown by other parameters, viz. (1) Northern Hemispheric surface temperature; (2) East-Pacific sea surface temperature; (3) El-Nino events and (4) Tahiti-Darwin pressure difference, and index of southern oscillation, over the 30-year samples analysed.

关键词： over Nino RELATIONSHIP BETWEEN 500 hPa RIDGE AXIS POSITIONS OVER THE indian AND THE WEST PACIFIC REGIONS AND THE indian SUMMER MONSOON RAINFALL

SIGNATURES OF UNIVERSAL CHARACTERISTICS OF FRACTAL FLUCTUATIONS IN GLOBAL MEAN MONTHLY TEMPERATURE ANOMALIES

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Journal of Systems Science & Complexity 2011年第1期24卷 14-38页

作者： A. M. SELVAM indian institute of tropical meteorology Pune 411008 India

This paper proposes a general systems theory for fractals visualising the emergence of successively larger scale fluctuations resulting from the space-time integration of enclosed smaller scale fluctuations. Global gridded time series data sets of monthly mean temperatures for the period 1880- 2007/2008 are analysed to show that data sets and corresponding power spectra exhibit distributions close to the model predicted inverse power law distribution. The model predicted and observed universal spectrum for interannual variability rules out linear secular trends in global monthly mean temperatures. Global warming results in intensification of fluctuations of all scales and manifested immediately in high frequency fluctuations.

关键词： Fractals and statistical normal distribution golden mean and fractal fluctuations long- range correlations and fat tail distributions power law distributions.

Use of Surface Observations to Estimate Upper Air Humidity for the Objective Analysis of Relative Humidity over indian Region

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Advances in Atmospheric Sciences 1990年第4期7卷 491-501页

作者： S.K.Sinha D.R.Talwalkar S.G.Narkhedkar P.L.Kulkarni S.Nair S.Rajamani indian institute of tropical meteorology pune-411008 india Indian Institute of Tropical Meteorology Pune-411008 IndiaIndian Institute of Tropical Meteorology Pune-411008 IndiaIndian Institute of Tropical Meteorology Pune-411008 IndiaIndian Institute of Tropical Meteorology Pune-411008 IndiaIndian Institute of Tropical Meteorology Pune-411008 India

In the present study objective analyses of relative humidity (RH) at surface and at the levels of 850, 700 and 500 hPa have been made using Gandin's (1963) optimum interpolation scheme. As the horizontal resolution of the radiosonde stations is rather inadequate for upper air humidity analysis, a scheme has been developed, following Rasmussen (1982) to estimate the upper air RH from the surface observations like surface RH, present weather and cloud cover. The relative humidities at the levels 850, 700 and 500 hPa were related to the surface observations through three separate regression relations. The RH values at 850, 700 and 500 hPa levels were estimated from the surface RH, cloud coverage and present weather using the above regression relations and subsequently the objective analyses at 00 GMT for the period from 4 July to 8 July 1979, were made using these estimated data along with the observed radiosonde data. Objective analyses were also made for the same period using only the radiosonde data for comparison to study the impact of those estimated data. Root mean square errors were computed for all the five days by interpolating RH at the observing stations from the objectively analysed field and comparing them with the actually observed RH to examine how best the analyses (with and without estimated data) fitted the observations. Lastly they were compared with satellite cloud pictures. This study shows that the estimated upper air RH values have positive impact on the analysis of upper air RH and could be used over radiosonde data sparse region and even over oceanic regions.

关键词： In RH over

Temperatures and Winds over tropical Middle Atmosphere during Two Contrasting Summer Monsoons, 1975 and 1979

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Advances in Atmospheric Sciences 1989年第3期6卷 325-334页

作者： B.K.Mukherjee C.P.Kulkarni K.Indira K.K.Dani indian institute of tropical meteorology Pune-411005IndiaIndian Institute of Tropical MeteorologyPune-411005IndiaIndian Institute of Tropical MeteorologyPune-411005IndiaIndian Institute of Tropical MeteorologyPune-411005India

Using the monthly geopotential heights and winds for 700 and 200 hPa for india during July and August, and the weekly M-100 Soviet rocketsonde temperature and wind data for Thumba (8.5 ° N, 76.9 ° E) during the last week of June and the first week of September for the two contrasting summer monsoon years 1975 (a very strong monsoon year) and 1979 (a very weak monsoon year), a study has been made to examine the mean circulation features of the troposphere over india, and the structures of the temperatures and the winds of the middle atmosphere over Thumba. The study suggested that the axis of the monsoon trough (AMT) at 700 hPa shifted southward in 1975 and northward towards the foothills of the Himalayas in 1979, from its normal position. Superimposed on the low-pressure area (AMT) at 700 hPa, a well-defined divergence was noticed at 200 hPa over the northern india in *** mean temperatures at 25,50 and 60 km (middle atmosphere) over Thumba were cooler in 1975 than in 1979. While a cooling trend in 1975 and warming trend in 1979 were observed at 25 and 50 km, a reversed picture was noticed at 60 km. There was a weak easterly / westerly (weak westerly phase) zonal wind in 1975 and a strong easterly zonal wind in 1979. A phase reversal of the zonal wind was observed at 50 km. A tentative physical mechanism was offered, in terms of upward propagation of the two equatorially trapped planetary waves i.e. the Kelvin and the mixed Rossby-gravity waves, to explain the occurrence of the two spells of strong warmings in the mesosphere in 1975.

关键词： over In and 1979 Temperatures and Winds over tropical Middle Atmosphere during Two Contrasting Summer Monsoons

Some Experiments with Multivariate Objective Analysis Scheme of Heights and Winds Using Optimum Interpolation

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Advances in Atmospheric Sciences 1992年第4期9卷 431-440页

作者： S.K.Sinha S.G.Narkhedkar D.R.Talwalkar S.Rajamani indian institute of tropical meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 India

A two-dimensional, multitvariate objective analysis scheme for simultaneous analysis of geopotential height and wind fields has been developed over indian and adjoining region for use in numerical weather prediction. The height-height correlations calculated using daily data of four July months (1976-1979), are used to derive the other autocorrelations and cross-correlations assuming geostropic relationship. A Gaussian function is used to model the autocorrelation function. Since the scheme is multivariate the regression coefficients (weights) are *** the equator, the geostrophic approximation relating mass and wind is decoupled in a way similar to Bergman (1979). The objective analyses were made over indian and adjoining region for 850, 700, 500, 300 and 200 hPa levels for the period from 4 July to 8 July 1979, 12 GMT. The analyses obtained using multivariate optimum interpolation scheme depict the synoptic situations satisfactorily. The analyses were also compared with the FGGE analyses (from ECMWF) and also with the station observations by computing the root mean square (RMS) errors and the RMS errors are comparable with those obtained in other similar studies.

关键词： In Some Experiments with Multivariate Objective Analysis Scheme of Heights and Winds Using Optimum Interpolation

Aircraft Observations of Electrical Conductivity in Warm Clouds

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Advances in Atmospheric Sciences 1993年第1期10卷 95-102页

作者： P.Ernest Raj P. C. S. Devara A. M. Selvam A. S. R. Murty indian institute of tropical meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 India

Aircraft observations of electrical conductivity and cloud microphsical, dynamical and other electrical parameters were made in warm stratocumulus and cumulus clouds forming during the summer monsoon seasons (June-September) of 1983 and 1985 in the Deccan Plateau region, india. A Gerdien type cylindrical condenser was used for the measurement of electrical conductivity. The variations in the electrical conductivity are observed to be closely associated with the updrafts and downdrafts in the cloud, liquid water content, cloud droplet charge and corona discharge current. The value of electrical conductivity in warm clouds is found to be in the order of 10-12 ohm-1 m-1 which is two orders higher than that observed in clear-air at cloud-base levels in some regions by other *** static electricity concepts predict reduced conductivity values inside clouds. Cloud electrical conductivity measurements, particularly in warm clouds are few and the results are contradictory. The recently identified mechanism of vertical mixing in clouds lends support to convective charge separation mechanism with inherent larger than clear-air values for cloud electrical conductivity and therefore consistent with the measurements reported herein.

关键词： Aircraft Observations of Electrical Conductivity in Warm Clouds

A Hydrometeorological Analysis of the Severe Rainstorm of 20-22 September 1900 over the Gangetic West Bengal

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Advances in Atmospheric Sciences 1993年第1期10卷 113-120页

作者： P. R. Rakhecha B. N. Mandal A. K. Kulkarni R. B. Sangam indian institute of tropical meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 IndiaIndian Institute of Tropical Meteorology Pune 411008 India

A hydrometeorological study is made of the September, 1900 severe rainstorm which led up to the record rainfalls over Gangetic West Bengal with subsequent disastrous flooding in the Damodar and the Hooghly rivers. The spatial extent of the rainstorm for different durations has been examined by constructing the isohyetal patterns based on rainfall records of stations affected by the storm. Areal rainfalls for 1,2 and 3-day periods are calculated and the values have been compared with similar values from other major rainstorms of the region. The comparison revealed that the September, 1900 rainstorm was the heaviest for 1,2 and 3-day durations for all the areas. The storm contributed rainfalls of 33.0 cm, 52.0 cm and 62.0 cm over an area of 10,000 km2 in 1,2 and 3 days respectively. This rainstorm could, therefore, be considered as an important input in flood and design storm studies in the Gangetic West Bengal region. A relationship between point to areal rainfall has also been developed with a view to evaluate areal PMP estimates.

关键词： A Hydrometeorological Analysis of the Severe Rainstorm of 20-22 September 1900 over the Gangetic West Bengal over West