scholarly journals Logistic Model as a Statistical Downscaling Approach for Forecasting a Wet or Dry Day in the Bagmati River Basin

2015 ◽  
Vol 9 (1) ◽  
pp. 9-22 ◽  
Author(s):  
Rajendra Man Shrestha ◽  
Srijan Lal Shrestha ◽  
Azaya Bikram Sthapit
Keyword(s):  
Relative Humidity ◽  
Sea Level ◽  
Principal Components ◽  
Logistic Model ◽  
Roc Analysis ◽  
Principal Component ◽  
Predictor Variables ◽  
Validation Period ◽  
Sea Level Pressure ◽  
Bagmati River

A binary logistic model is developed for probabilistic prediction of a wet or dry day based upon daily rainfall data from 1981 to 2008 taken from 25 stations of Bagmati River basin. The predictor variables included in the model are daily relative humidity, air surface temperature, sea level pressure, v-wind which are expressed as principal components of 9 grids of the National Centers for Environmental Protection (NCEP)/National Center for Atmospheric Research (NCAR) Reanalysis data with resolution of 2.50×2.50. Principal component analysis is used to reduce the dimension of the predictors in the presence of spatial correlations between grids and thus reduce their multicollinearity effect. The result depicts that the model has 86.4 percent predictive capability in the analysis period (1981-2000) and 86.1 in the validation period (2001-2008) along with support of receiver operating characteristic (ROC) analysis. The results demonstrate that the first two principal components of relative humidity are the key predictor variables with respective odds ratios (ORs) of 4.18 and 3.61, respectively. The other statistically significant predictors are the second principal component of v-wind with OR 1.43, the second and first principal components of air surface temperature with ORs 1.38 and 0.76, respectively and the first principal component of sea level pressure with OR 0.44. Goodness-of-fit test, ROC analysis and other main diagnostic tests showed that the fitted logistic model is characterized by good fits for analysis as well as validation period.

scholarly journals Recent atmospheric changes and future projections along the Saudi Arabian Red Sea Coast

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Abdulhakim Bawadekji ◽  
Kareem Tonbol ◽  
Nejib Ghazouani ◽  
Nidhal Becheikh ◽  
Mohamed Shaltout
Keyword(s):  
Relative Humidity ◽  
Sea Level ◽  
Air Temperature ◽  
Surface Wind ◽  
Surface Air Temperature ◽  
Saudi Arabian ◽  
Sea Level Pressure ◽  
Ensemble Mean ◽  
Red Sea Coast ◽  
Sea Coast

AbstractRecent and future climate diagrams (surface air temperature, surface relative humidity, surface wind, and mean sea level pressure) for the Saudi Arabian Red Sea Coast are analysed based on hourly observations (2016–2020) and hourly ERA5 data (1979–2020) with daily GFDL mini-ensemble means (2006–2100). Moreover, GFDL mini-ensemble means are calculated based on the results of three GFDL simulations (GFDL-CM3, GFDL-ESM2M, and GFDL-ESM2G). Observation data are employed to describe the short-term current weather variability. However, ERA5 data are considered to study the long-term current weather variability after bias removal via a comparison to observations. Finally, a bias correction statistical model was developed by matching the cumulative distribution functions (CDFs) of corrected ERA5 and mini-ensemble mean data over 15 years (2006–2020). The obtained local statistic were used to statically downscale GFDL mini-ensemble means to study the future uncertainty in the atmospheric parameters studied. There occurred significant spatial variability across the study area, especially regarding the surface air temperature and relative humidity, based on monthly analysis of both observation and ERA5 data. Moreover, the results indicated that the ERA5 data suitably describe Tabuk, Jeddah and Jizan weather conditions with a marked spatial variability. The best performance of ERA5 surface air temperature and relative humidity (surface wind speed and sea level pressure) data was detected in Tabuk (Jeddah). These data for the Saudi Arabian Red Sea coast, 1979–2020, exhibit significant positive trends of the surface air temperature and surface wind speed and significant negative trends of the relative humidity and sea level pressure. The GFDL mini-ensemble mean projection result, up to 2100, contains a significant bias in the studied weather parameters. This is partly attributed to the coarse GFDL resolution (2° × 2°). After bias removal, the statistically downscaled simulations based on the GFDL mini-ensemble mean indicate that the climate in the study area will experience significant changes with a large range of uncertainty according to the considered scenario and regional variations.

DETERMINATION OF THE CORRELATION BETWEEN INDIVIDUAL METEOROLOGICAL VALUES AT THE BEGINNING OF THE DEPOSITION OF ICE ON THE TERRITORY OF UKRAINE BY THE MONTHS OF THE COLD PERIOD OF THE YEAR DURING 2001-2013 AND THEIR SPATIAL DISTRIBUTION

2019 ◽  
pp. 140-151
Author(s):  
S.I. Pyasetska ◽  
N.P. Grebenyuk ◽  
S.V. Savchuk
Keyword(s):  
Wind Speed ◽  
Relative Humidity ◽  
Sea Level ◽  
Meteorological Parameters ◽  
Cold Period ◽  
Sea Level Pressure ◽  
Average Maximum ◽  
Average Relative Humidity ◽  
Maximum Minimum

The article presents the results of the study of the determination of the correlation connection between a number of meteorological values at the beginning of the deposition of ice on the wires of a standard ice-cream machine in certain months of the cold period of the year on the territory of Ukraine during 2001-2013. The research was conducted for 3 winter months, as well as for March and November. The pair of meteorological parameters have been determined at the beginning of the deposition of ice that have a statistically significant correlation coefficient and a spatial-temporal distribution of the distribution in certain months across the territory of Ukraine has been obtained. The most common variant of the statistically significant connection between individual meteorological parameters was the connection between the temperature of the water column (average, maximum, minimum) and relative humidity of air (average, maximum). Thus, for almost all months studied, a statistically significant correlation between the temperature of the vapor (average, maximum, minimum) and relative humidity of air (average, maximum) was established. For the winter months, the correlation coefficient of this connection was positive, and for March and November, it was negative. A widespread version of a statistically significant connection was the relationship between the air temperature (average, maximum, minimum) and the height of the snow cover. This connection for the months studied turned out to be negative. The variants of negative statistically significant connection between average wind speed and average relative humidity of air (January-February, December), average and maximum wind speed and sea-level pressure (November), and also between daily amount precipitation and snow (March), daily rainfall and wind speed (average, maximum), and pressure at sea level (November). During the months of the cold period of the year, statistically significant connections between the air temperature (average, maximum) and pressure at sea level (November), wind speed (average, maximum) and average humidity (January, December), pressure on sea levels and average relative humidity (March). Also, there were isolated cases of statistically significant correlation between snow and sea level pressure (December). The most frequently statistically significant connections between meteorological values at the dates of deposition of ice on the wires of a standard icing machine were observed at stations in the central, northeastern, eastern and separate southern regions.

scholarly journals Studying Recorded lightning over Iraq for Period 1998-2011

2018 ◽  
Vol 28 (3) ◽  
pp. 1
Author(s):  
Lena Mohammed Abbas
Keyword(s):  
Relative Humidity ◽  
Sea Level ◽  
Vertical Velocity ◽  
Mean Value ◽  
Sea Level Pressure ◽  
Mean Sea Level ◽  
Mean Values ◽  
Level Pressure ◽  
Special Cases ◽  
The Hours

This research studies distribution of thunderstorm in Iraq for the period (1998-2011), the result showed that  the largest regions which had been hit by lightning stroke were between latitude (35-36◦)E and longitude (45-46◦)N, and April was the most frequent of lightning occurrence, also the results showed  that the number of flashes of most lightning cases were between (50-100) with higher number of flashes for some special cases. The studying of meteorological parameters which accompanied thunderstorm formation such as (Mean sea level pressure, Lifting index, relative humidity and Vertical velocity) illustrates the values of mean sea level pressure were increased during the hours after lightning occurrence comparing with their values before and at the time of lightning occurrence and their monthly mean value much greater than that recorded at the time of lightning occurrence, in addition the values of lifting index were negative at the time of lightning occurrence that refer to instability whereas their monthly average showed positive values. The values of relative humidity were greater at lightning recorded time at the three levels (500, 700, 1000)mb and also through the hours before and after this time comparing with their monthly mean. Vertical velocity values were negative for the three levels at the time of lightning occurrence that is referring to upward motion which is necessary for thundercloud initiation, and their monthly mean values were mostly negative at (500, 700)mb whereas were positive at the surface level

Complex principal component analysis of sea-level pressure over the eastern USA

2007 ◽  
Vol 11 (1) ◽  
pp. 27-54 ◽  
Author(s):  
Jerry M. Davis ◽  
Frank L. Estis ◽  
Peter Bloomfield ◽  
John F. Monahan
Keyword(s):  
Principal Component Analysis ◽  
Sea Level ◽  
Principal Component ◽  
Component Analysis ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
Eastern Usa

scholarly journals Wet-Bulb Temperature from Relative Humidity and Air Temperature

2011 ◽  
Vol 50 (11) ◽  
pp. 2267-2269 ◽  
Author(s):  
Roland Stull
Keyword(s):  
Gene Expression ◽  
Relative Humidity ◽  
Sea Level ◽  
Air Temperature ◽  
Mean Absolute Error ◽  
Gene Expression Programming ◽  
Absolute Error ◽  
Sea Level Pressure ◽  
Air Temperatures ◽  
Low Humidity

AbstractAn equation is presented for wet-bulb temperature as a function of air temperature and relative humidity at standard sea level pressure. It was found as an empirical fit using gene-expression programming. This equation is valid for relative humidities between 5% and 99% and for air temperatures between −20° and 50°C, except for situations having both low humidity and cold temperature. Over the valid range, errors in wet-bulb temperature range from −1° to +0.65°C, with mean absolute error of less than 0.3°C.

Climatological Characteristics of Heavy Rainfall in Northern Pakistan and Atmospheric Blocking over Western Russia

2016 ◽  
Vol 29 (21) ◽  
pp. 7743-7754 ◽  
Author(s):  
Tomohito J. Yamada ◽  
Daiki Takeuchi ◽  
M. A. Farukh ◽  
Yoshikazu Kitano
Keyword(s):  
Sea Level ◽  
Heavy Rainfall ◽  
Principal Component ◽  
Heavy Precipitation ◽  
Boreal Summer ◽  
Northern Pakistan ◽  
Atmospheric Blocking ◽  
Sea Level Pressure ◽  
Level Pressure

Abstract Pakistan and northwestern India have frequently experienced severe heavy rainfall events during the boreal summer over the last 50 years including an event in late July and early August 2010 due to a sequence of monsoon surges. This study identified five dominant atmospheric patterns by applying principal component analysis and k-means clustering to a long-term sea level pressure dataset from 1979 to 2014. Two of these five dominant atmospheric patterns corresponded with a high frequency of the persistent atmospheric blocking index and positive sea level pressure over western Russia as well as an adjacent meridional trough ahead of northern Pakistan. In these two groups, a negative sea surface temperature anomaly was apparent over the equatorial mid- to eastern Pacific Ocean. The heavy precipitation periods with high persistent blocking frequency in western Russia as in the 2010 heat wave tended to have 1.2 times larger precipitation intensity compared to the whole of the heavy precipitation periods during the 36 years.

scholarly journals Study of Some Patterns for Severe Rainfalls Over Iraq

2020 ◽  
Vol 31 (4) ◽  
pp. 9
Author(s):  
Yaser Ali Shaghati
Keyword(s):  
Relative Humidity ◽  
Sea Level ◽  
Vertical Velocity ◽  
Geopotential Height ◽  
Cloud Cover ◽  
Heavy Rain ◽  
Relative Vorticity ◽  
Sea Level Pressure ◽  
First Case ◽  
Heavy Rainfalls

Study of rain received particularly great importance in the areas described as semi-arid, which is on the other hand are not well prepared for the drainage of rain that may turned into flash floods. The pressure systems, especially those passing through the country in the winter rainy season and spring also autumn have a role in determining the amount of rainfall falling in the region In addition to climate change and its effects in terms of climate cycles and climate extremes and thus required determine the size of rainfall Whether it is beneficial or harmful. In this study to determine of heavy rainfalls, two important cases of heavy rainfalls were studied in 24, Dec, 2016 and 24, Nov, 2018, which exceeded 50 mm on the Iraq, from one country to another in this account , rainfalls rate, divider from the World Meteorological Organization (WMO) in which the rain intensity is determined according to the schedule and limits (light precipitation I≤2 mm / hour), (moderate precipitation 2<I≤10 mm / Hour), (heavy precipitation 10 <I≤50 mm / hour), (torrential precipitation I> 50 mm / hour). Each case was Analyzed and visualized by using the data analysis and display system (GrADS) The data were obtained from Tropical Rainfall Measuring Mission (TRMM). Show maps results of the first case in (24 December, 2016) in the northeastern region, the central region and the western region of the country the abundant rain condition through maps of rainfall rates on these areas as well as by maps of mean sea level pressure and dense cloud cover, maps showed a decrease the temperature accompanying the low pressure also streamlines, geopotential height, relative vorticity show this. And show the vertical velocity (omega), relative humidity, geopotential height, relative vorticity, and show support of air decline in terms of streamlines, relative humidity, geopotential height and relative vorticity over the country. Maps 700 hPa the vertical velocity (omega), relative humidity, geopotential height and relative vorticity, maps 500 hPa, results of second case, (24 November, 2018) that occurred in the northeastern and eastern part and southeastern part of the country, also appear clear through maps of falling rainfall rates, as well as maps of sea level pressure and the dense cloud cover accompanying the heavy rain situation. maps 850 hPa it shows the low temperature accompanying the atmospheric decline, also streamlines, geopotential height and relative vorticity also maps 700 hPa and 500 hPa lik first case, in differential patterns all of this shows clear support for the atmospheric decline in terms of streamlines, relative humidity, geopotential height, and relative vorticity, and explain the causes of heavy rain situation over Iraq.

scholarly journals Historical SAM Variability. Part I: Century-Length Seasonal Reconstructions*

2009 ◽  
Vol 22 (20) ◽  
pp. 5319-5345 ◽  
Author(s):  
Julie M. Jones ◽  
Ryan L. Fogt ◽  
Martin Widmann ◽  
Gareth J. Marshall ◽  
Phil D. Jones ◽  
...  
Keyword(s):  
Sea Level ◽  
Southern Hemisphere ◽  
Austral Summer ◽  
Principal Component ◽  
Reanalysis Data ◽  
The Other ◽  
Considerable Variability ◽  
Sea Level Pressure ◽  
Level Pressure ◽  
The Individual

Abstract Seasonal reconstructions of the Southern Hemisphere annular mode (SAM) index are derived to extend the record before the reanalysis period, using station sea level pressure (SLP) data as predictors. Two reconstructions using different predictands are obtained: one [Jones and Widmann (JW)] based on the first principal component (PC) of extratropical SLP and the other (Fogt) on the index of Marshall. A regional-based SAM index (Visbeck) is also considered. These predictands agree well post-1979; correlations decline in all seasons except austral summer for the full series starting in 1958. Predictand agreement is strongest in spring and summer; hence agreement between the reconstructions is highest in these seasons. The less zonally symmetric SAM structure in winter and spring influences the strength of the SAM signal over land areas, hence the number of stations included in the reconstructions. Reconstructions from 1865 were, therefore, derived in summer and autumn and from 1905 in winter and spring. This paper examines the skill of each reconstruction by comparison with observations and reanalysis data. Some of the individual peaks in the reconstructions, such as the most recent in austral summer, represent a full hemispheric SAM pattern, while others are caused by regional SLP anomalies over the locations of the predictors. The JW and Fogt reconstructions are of similar quality in summer and autumn, while in winter and spring the Marshall index is better reconstructed by Fogt than the PC index is by JW. In spring and autumn the SAM shows considerable variability prior to recent decades.

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