scholarly journals Statistical analysis of monsoon rainfall distribution over West Bengal, India

MAUSAM ◽  
2021 ◽  
Vol 61 (4) ◽  
pp. 487-498
Author(s):  
AVIK GHOSH DASTIDAR ◽  
SARBARI GHOSH ◽  
U. K. DE ◽  
S. K. GHOSH

Seasonal, monthly and daily rainfall characteristics of meteorological sub-divisions of Sub Himalayan West Bengal (SHWB) and Gangetic West Bengal (GWB) have been studied using rainfall data of 23 stations of India Meteorological Department (IMD) over the state of West Bengal. The two subdivisions have distinctive characteristics, though two stations lying in the plain region of SHWB have behaviour more alike the stations of GWB.  Krishnagar is a station with least seasonal rainfall in the entire state. Kurtosis and Skewness of the seasonal rainfall distribution have been studied and found that, for most of the stations they lie within reasonable limits. From the time series analysis, it is found that the seasonal rainfall has no trend.     

2010 ◽  
Vol 49 (12) ◽  
pp. 2559-2573 ◽  
Author(s):  
Matthew G. Slocum ◽  
William J. Platt ◽  
Brian Beckage ◽  
Steve L. Orzell ◽  
Wayne Taylor

Abstract Wildfires are often governed by rapid changes in seasonal rainfall. Therefore, measuring seasonal rainfall on a temporally finescale should facilitate the prediction of wildfire regimes. To explore this hypothesis, daily rainfall data over a 58-yr period (1950–2007) in south-central Florida were transformed into cumulative rainfall anomalies (CRAs). This transformation allowed precise estimation of onset dates and durations of the dry and wet seasons, as well as a number of other variables characterizing seasonal rainfall. These variables were compared with parameters that describe ENSO and a wildfire regime in the region (at the Avon Park Air Force Range). Onset dates and durations were found to be highly variable among years, with standard deviations ranging from 27 to 41 days. Rainfall during the two seasons was distinctive, with the dry season having half as much as the wet season despite being nearly 2 times as long. The precise quantification of seasonal rainfall led to strong statistical models describing linkages between climate and wildfires: a multiple-regression technique relating the area burned with the seasonal rainfall characteristics had an of 0.61, and a similar analysis examining the number of wildfires had an of 0.56. Moreover, the CRA approach was effective in outlining how seasonal rainfall was associated with ENSO, particularly during the strongest and most unusual events (e.g., El Niño of 1997/98). Overall, the results presented here show that using CRAs helped to define the linkages among seasonality, ENSO, and wildfires in south-central Florida, and they suggest that this approach can be used in other fire-prone ecosystems.


Author(s):  
Gadekar Deepak Janardhan ◽  
Soniya Sonkar

The three major characteristics of rainfall are mainly its amount, frequency and intensity. The value of rainfall varies greatly from day to day, place to place, month and year to year. Generally Akole tehsil receives the highest rainfall and Karjat and Jamkhed tehsils receives the least rainfall. The main reason for the highest rainfall in Akole tehsil is orographic type rainfall. The rainfall characteristics and distribution in drought prone area in study area. The research covers rainfall data from 1981 to 2014 and the rainfall data is taken from the statistical department website of Ahmednagar district.


2018 ◽  
Vol 22 (10) ◽  
pp. 5259-5280 ◽  
Author(s):  
Hannes Müller-Thomy ◽  
Markus Wallner ◽  
Kristian Förster

Abstract. In this study, the influence of disaggregated rainfall products with different degrees of spatial consistence on rainfall–runoff modeling results is analyzed for three mesoscale catchments in Lower Saxony, Germany. For the disaggregation of daily rainfall time series into hourly values, a multiplicative random cascade model is applied. The disaggregation is applied on a station by station basis without consideration of surrounding stations; hence subsequent steps are then required to implement spatial consistence. Spatial consistence is represented here by three bivariate spatial rainfall characteristics that complement each other. A resampling algorithm and a parallelization approach are evaluated against the disaggregated time series without any subsequent steps. With respect to rainfall, clear differences between these three approaches can be identified regarding bivariate spatial rainfall characteristics, areal rainfall intensities and extreme values. The resampled time series lead to the best agreement with the observed ones. Using these different rainfall products as input to hydrological modeling, we hypothesize that derived runoff statistics – with emphasis on seasonal extreme values – are subject to similar differences as well. However, an impact on the extreme values' statistics of the hydrological simulations forced by different rainfall approaches cannot be detected. Several modifications of the study design using rainfall–runoff models with and without parameter calibration or using different rain gauge densities lead to similar results in runoff statistics. Only if the spatially highly resolved rainfall–runoff WaSiM model is applied instead of the semi-distributed HBV-IWW model can slight differences regarding the seasonal peak flows be identified. Hence, the hypothesis formulated before is rejected in this case study. These findings suggest that (i) simple model structures might compensate for deficiencies in spatial representativeness through parameterization and (ii) highly resolved hydrological models benefit from improved spatial modeling of rainfall.


MAUSAM ◽  
2022 ◽  
Vol 44 (4) ◽  
pp. 353-358
Author(s):  
B. BISWAS ◽  
K. GUPTA

Monthly and seasonal variations of southwest monsoon rainfall over the districts of Gangetic and Sub-Himalayan West Bengal are presented and their differences discussed. Latitudinal variations of monsoon rainfall are brought out. Decadal means of seasonal rainfall over plains are compared with those at higher elevations and northern latitudes. An attempt is made to study long term rainfall trends.


2021 ◽  
Vol 1 (2) ◽  
pp. 123-135
Author(s):  
Abdullahi Umar ◽  
Saadu Umar Wali ◽  
Ibrahim Mustapha Dankani

Wavelet transform has been underutilized in characterization of rainfall (Real Onset Dates and Real Cessation Dates) in the study area. This study aims at the characterization of monsoonal rainfall. Daily rainfall data of four stations for the period 1981-2018 were collected from Nigerian Meteorological Agency. The Intra-seasonal Rainfall Monitoring Index (IRMI) was generated and used in determining the RODs and RCDs. The Mann–Kendall test was used to detect trends of the rainfall characteristics. Wavelet transform was used in modelling RODs and RCDs. Findings revealed that RODs vary between stations. There is low (0.3 Spearman’s Rank r) correlation between latitudes and Early Cessations (ECs) of rains. The Morlet wavelet analysis revealed that from 1999 to 2018, there were more of EOs and NOs especially in Kano station. We conclude that from 1981 to 2018 there has been a minimal increase in the retreat dates of rainfall in the study area.


2017 ◽  
Vol 7 (4) ◽  
pp. 30 ◽  
Author(s):  
Jurgen D. Garbrecht ◽  
Rabi Gyawali ◽  
Robert W. Malone ◽  
John C. Zhang

Long-term observations of daily rainfall are common and routinely available for a variety of hydrologic applications. In contrast, observations of 10 or more years of continuous hourly rainfall are rare. Yet, sub-daily rainfall data are required in rainfall-runoff models. Rainfall disaggregation can generate sub-daily time-series from available long term daily observations. Herein, the performance of Multiplicative Random Cascade (MRC) model at disaggregating daily-to-hourly rainfall was investigated. The MRC model was parameterized and validated with 15 years of continuous observed daily and hourly rainfall data at three weather stations in Oklahoma. Model performance, or degree to which the disaggregated rainfall time series replicated observations, was assessed using 46 variables of hourly rainfall characteristics, such as longest wet spell duration, average number of rainfall hours per year, and largest hourly rainfall. Findings include: a) average-type hourly rainfall characteristics were better replicated than single value characteristics such as longest, maximum, or peak hourly rainfall; b) the large number of sub-trace hourly rainfall values (<0.254 mm h-1) generated by the MRC model were not supported by observations; c) the random component of the MRC model led to a variation under 15% of the average value for most rainfall characteristics with the exceptions of the “longest wet spell duration” and “maximum hourly rainfall”; and d) the MRC model produced fewer persistent rainfall events compared to those in the observed rainfall record. The large number of generated trace rainfall values and difficulties to replicate reliably extreme rainfall characteristics, reduces the number of potential hydrologic applications that could take advantage of the MRC disaggregated hourly rainfall. Nevertheless, in most cases, the disaggregated rainfall generated by the MRC model replicated observed average-type rainfall characteristics well.


MAUSAM ◽  
2021 ◽  
Vol 48 (1) ◽  
pp. 71-76
Author(s):  
V. JAYASREE ◽  
K.G. ANIL KUMAR

ABSTRACT. The daily rainfall distribution of twelve stations in the Chalakudy river basin of central Kerala is studied. Normalised rainfall curve (NRC) is constructed and various parameters of the daily rainfall distribution are derived. The number of rainy days and mean rain intensities at each 10% rain amounts are calculated from the NRC. It has been found that the coefficient of variation (CY) is the most important parameter of the daily rainfall distribution which determines the shape of NRC. Frequency distribution of CY values reveals that the CY is highest in the range of 100-120%. Rainfall contributions by non-rainy days and significant rainfall days are calculated. About half of the seasonal rainfall which contributes 80% of the total rainfall are of low intensity. However, the remaining 20% due to higher intensity rainfall are of considerable significance for floods, erosion, etc.    


MAUSAM ◽  
2021 ◽  
Vol 72 (3) ◽  
pp. 545-552
Author(s):  
PRAMITI KUMAR CHAKRABORTY ◽  
LALU DAS

Monsoon rainfall is the dominant factor that determines the success or failure of agriculture in general. Gangetic West Bengal is not any exception. Monsoon rainfall has immense importance for growing kharif rice in this region. Whereas pre-monsoon rainfall helps farmers for proper crop planning like choosing variety etc. So assessing a long (1901-2005) and short (1961-2005 and 1991-2005) period rainfall data, its comparison with different models and construction of future scenario have utmost importance. For this purpose, rainfall data from nine selected station of India Meteorological Department were collected and subjected to trend analysis. Model outputs were compared with the observed station data. Results showed an overall negative trend of pre-monsoon rainfall during 1901-2005. However, increasing trend in monsoon rainfall was noticed during the same period. In future scenario, monsoon rainfall indicates a nominal increase (~6%) whereas pre-monsoon rainfall increases in moderate amount (~11%). So, from the study it may be said that in near future farmers and crop planner should give more importance in pre-monsoon rainfall for better crop planning and other stake holder activities.


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