Forecasting precipitation over Delhi during the south-west monsoon season

The south-west monsoon (June-September) is the major rainy season over India. Information about the occurrence of precipitation and the expected quantity at a specific place is important in many sectors of human activity. In this study, objective methods are developed to forecast the probability of precipitation (POP) and provide the quantity of precipitation forecast (QPF) over Delhi. As the onset of the monsoon at Delhi is around 30 June, the models are developed for the months of July, August and September (JAS) using surface and upper-air data for the period 1985-90 and tested with data from JAS for 1994 and 1995. A multiple linear regression equation is developed to forecast the POP and multiple discriminant analysis is used to produce the QPF in terms of one of four groups (0.1-1.0; 1.1-10.0; 10.1-30.0; and ≥30.1 mm). The QPF model is used only if precipitation is expected to occur (the POP forecast is turned into a categorical forecast). The categorical forecasts based on the POP exhibit positive skill scores consistently with both the development and independent data sets. The model for QPF also performed satisfactorily

Statistical model-based forecast of minimum and maximum temperatures at Manali

Various types of avalanches frequent northwest Himalayan regions during winter months. Winter season over this region is frequented by westwardmoving weather systems called western disturbances (WDs). These weather systems yield enormous amount of precipitation. Knowledge of minimum and maximum temperatures during winter months is very useful for assessing human and natural hazards. Models for forecasting minimum and maximum temperatures have been developed for Manali in Himanchal Pradesh, for the months of December, January and February. These models are based on statistical techniques and use surface and upper air meteorological data from 1984 to 1989. The models are also tested with independent data and the results for 1995-96 are presented. The models yield good results with independent cases providing about 88% correct forecast within ±2°C of the observed values

Prediction of precipitation associated with a western disturbance using a high-resolution regional model: role of parameterisation of physical processes

In this study a non-hydrostatic version of the PSU/NCAR mesoscale model is used to simulate an active western disturbance (WD) that affected the Indian region in January 1997. The role of the planetary boundary layer (PBL) and convection parameterisation schemes in the development of the WD is investigated. Analysis and predictions for some fields, including sea level pressure, geopotential height, temperature, horizontal wind and precipitation are examined. Some statistical scores are also calculated and compared. It is found that the performance of the Hong-Pan (as implemented in the NCAR MRF model) and Betts-Miller (or Grell) schemes as PBL and convection parameterisation schemes respectively are best compared to the other schemes used in this study

A study on dynamic and thermodynamic aspects of breaks in the summer monsoon over India

The rainfall associated with the Indian summer monsoon shows large intraseasonal and interannual variability. Break-monsoon conditions are one of the important epochs of the monsoon, and they contribute significantly to the intraseasonal variability of the monsoon. The National Centers for Environmental Prediction-National Center for Atmospheric Research reanalysis data sets are used to investigate the significant energy budget terms during the pre-break (5 days prior to the commencement of the break), break and post-break (5 days after the cessation of the break) periods. In the present study, certain dynamic and thermodynamic characteristics of the monsoon circulation during break-monsoon conditions are investigated. The important terms in the various energy budget equations are analysed between the surface and 100 hPa for the break and its departures from pre- and post-break for the period 1968-96. The statistical significance of these departures is also examined by Student's t-test at the 95% confidence level. The volume integral of the budget terms is also examined in four sectors, i.e. the Arabian Sea, Bay of Bengal, northern India and central India. Significant changes in the wind field and vorticity at 850 hPa take place in the monsoon trough zone, coastal regions of the western coast of India and the southwestern Bay of Bengal off the southern Indian coast. The vertically upward rising arm of the Hadley cell weakens during the break phase. The strong flux convergence of kinetic energy in the central Arabian Sea and flux divergence in the northeastern Bay of Bengal weakens during pre- and post-break periods. Significant changes in the diabatic heating horizontal flux of heat and moisture are observed in the monsoon trough zone, central and northwestern Bay of Bengal. The Bay of Bengal and central India sectors show higher magnitudes and changes in respect of dynamic and thermodynamic parameters compared with the Arabian Sea and northern India

Forecasting minimum temperature during winter and maximum temperature during summer at Delhi

A knowledge of minimum temperature during winter and maximum temperature during summer is a very useful for individuals, as well as for organisations whose workers and machines have to operate in the open, e.g. the armed forces, railways, roadways, tourism, etc. Accurate forecasts of minimum temperature during winter help in the prediction of cold-wave conditions and those of maximum temperature during summer help in the prediction of heat-wave conditions over northern India. Models for forecasting the minimum temperature during December and the maximum temperature during May at Delhi have been developed using surface and upper-air meteorological data from 1984-89. The results of testing the models on independent data from recent years (1994-95) are presented. The results are encouraging and more than 80% of the forecasts are correct within ±2°C. Possible reasons for large deviations are also investigated

Forecasting of thunderstorms in the pre-monsoon season at Delhi

Accurate prediction of thunderstorms during the pre-monsoon season (April-June) in India is essential for human activities such as construction, aviation and agriculture. Two objective forecasting methods are developed using data from May and June for 1985-89. The developed methods are tested with independent data sets of the recent years, namely May and June for the years 1994 and 1995. The first method is based on a graphical technique. Fifteen different types of stability index are used in combinations of different pairs. It is found that Showalter index versus Totals total index and Jefferson's modified index versus George index can cluster cases of occurrence of thunderstorms mixed with a few cases of non-occurrence along a zone. The zones are demarcated and further sub-zones are created for clarity. The probability of occurrence/non-occurrence of thunderstorms in each sub-zone is then calculated. The second approach uses a multiple regression method to predict the occurrence/nonoccurrence of thunderstorms. A total of 274 potential predictors are subjected to stepwise screening and nine significant predictors are selected to formulate a multiple regression equation that gives the forecast in probabilistic terms. Out of the two methods tested, it is found that the multiple regression method gives consistently better results with developmental as well as independent data sets; it is a potential method for operational use

Coherence Resonance in Chaotic Systems

We show that it is possible for chaotic systems to display the main features of coherence resonance. In particular, we show that a Chua model, operating in a chaotic regime and in the presence of noise, can exhibit oscillations whose regularity is optimal for some intermediate value of the noise intensity. We find that the power spectrum of the signal develops a peak at finite frequency at intermediate values of the noise. These are all signatures of coherence resonance. We also experimentally study a Chua circuit and corroborate the above simulation results. Finally, we analyze a simple model composed of two separate limit cycles which still exhibits coherence resonance, and show that its behavior is qualitatively similar to that of the chaotic Chua systemComment: 4 pages (including 4 figures) LaTeX fil

Microwave Gaseous Discharges

Contains research objectives and reports on five research projects

Genetic Introgression and the Survival of Florida Panther Kittens

Estimates of survival for the young of a species are critical for population models. These models can often be improved by determining the effects of management actions and population abundance on this demographic parameter. We used multiple sources of data collected during 1982–2008 and a live-recapture dead-recovery modeling framework to estimate and model survival of Florida panther (Puma concolor coryi) kittens (age 0–1 year). Overall, annual survival of Florida panther kittens was 0.323 ± 0.071 (SE), which was lower than estimates used in previous population models. In 1995, female pumas from Texas (P. c. stanleyana) were released into occupied panther range as part of an intentional introgression program to restore genetic variability. We found that kitten survival generally increased with degree of admixture: F1 admixed and backcrossed to Texas kittens survived better than canonical Florida panther and backcrossed to canonical kittens. Average heterozygosity positively influenced kitten and older panther survival, whereas index of panther abundance negatively influenced kitten survival. Our results provide strong evidence for the positive population-level impact of genetic introgression on Florida panthers. Our approach to integrate data from multiple sources was effective at improving robustness as well as precision of estimates of Florida panther kitten survival, and can be useful in estimating vital rates for other elusive species with sparse data

Important synoptic features during INDOEX IFP-99

INDOEX IFP-99 was undertaken as part of the international experiment in the Indian Ocean to take observations pertaining to aerosols, radiation, cloud physics and other related meteorological parameters. The important-aim of the INDOEX was to quantify radiative forcing due to natural and anthropogenic aerosols and their feedback on regional and global climate systems. Since prevailing circulation features transports aerosols, it is essential that important synoptic patterns during the expedition phase, i.e. 20 January to 10 March 1999 be examined. Based on the synoptic features it was noticed that crossequatorial flow in lower levels from western Arabian Sea to southern Indian Ocean was significantly higher than the eastern Arabian Sea. Two cyclonic storms, one in the south Bay of Bengal during 1-3 February and another in the south Indian Ocean during 4-13 March were observed. Significant changes in the cross-equatorial flow in the lower/upper tropospheric levels and ITCZ locations were noticed