Air pollution is a problem in Kathmandu, Nepal. Particulate matter concentrations often exceed threshold values at which human health is severely affected. The problem is serious since it is in the valley topography wherein the meteorological parameters role is significant. This study addresses the linkages between meteorological processes and air pollution in the lower atmosphere of the Kathmandu Valley. The study establishes influence of meteorological conditions like temperature, rainfall, humidity, atmospheric pressure, wind direction and speed with elemental concentrations of PM10 in Kathmandu Valley. Government of Nepal has established permanent air monitoring stations in the valley and a continuous PM10 data is available on the public domain. The data relating to average daily temperature, rainfall, humidity, atmospheric pressure, wind speed and wind direction recorded in Tribhuvan International Airport was used for analysis. The mean association of PM10 levels and meteorological parameters during the period of March 2003 and December 2005 is established. Pearson’s coefficient of correlation was applied to study the association between PM10 and meteorological variables. The atmospheric pressure, wind velocity and humidity was found to be significant factors compared to others influencing PM10. Increase of rainfall and humidity has negative correlation with average PM10 concentration in Kathmandu valley. The study also infers that the wind speed and atmospheric pressure inducing increment of average PM10 concentration in Kathmandu Valley.

Drought management is very important for optimal water resources application in arid and semi-arid regions. One strategy to manage drought is to predict drought conditions by probabilistic tools. In this study, total monthly precipitation records related to 33 synoptic stations of Iran during 1976-2005 were used to monitor and predict future drought conditions. Regarding the dry periods greater than six months in the arid regions of the country, the Standardized Precipitation Index (SPI) at 6-month timescale was used for drought monitoring. The first-order Markov chain model was employed to predict drought condition up to 3-step ahead. This model was fitted on the SPI series at all stations of interest, and it was identified that can represent the probabilistic behavior of drought over Iran. The results obtained from drought prediction at 1, 2, and 3-step ahead over Iran showed that the occurrence of the severe drought (9 percent of stations) or normal conditions (87 percent of stations) is most probable in the future months, regardless of drought condition at current month. Also, drought monitoring based on aerial mean of monthly total precipitation time series over country showed that the trend of drought severity has been increasing in recent years.

In this paper meteorological conditions of some acute air pollution periods for the city of Tehran have been considered. The data used, were obtained from the Air Quality Control Company (AQCC) of Tehran Municipality and from synoptic station of the Institute of Geophysics, university of Tehran. Initially some statistical methods were used to find the episodes for acute air pollution episodes, and then their meteorological conditions were considered.One suitable method for determining acute air pollution episodes is the use of P parameter which is defined as the number of events in which the air pollution concentrations is 1.5 times (and more than) the averaged seasonal mean. A typical case for this study for P value is shown in figure (1) in which a bubble structure between polar and subtropical jet streams over the area, (see below) has led to large values of showing an acute air pollution episode.

The air pollution in Tehran is a significant problem that needs to be studied carefully in various aspects. Meteorological conditions leading to acute air pollution episode are particularly important to be studied. Period of this study has been chosen from 2001 till 2002. Azadi, Bahman, Tajrish, Markazi and Gholhak air pollution monitoring stations were chosen to cover Tehran almost completely.In this study the daily changes of pollutants in cold seasons are examined. This includes time variations of pollutants in Tehran such as CO, NOx, and SO2 in all stations. This analysis showed that during the synoptic conditions (high pressure systems) the amount of air pollutants have increased for several days and reached to their highest levels of concentration. These levels may exceed two to three times the limits.

One of the most important factors in calculation of greenhouse crop water requirement is the accurate estimation of reference crop evapotranspiration. Numerous parameters affect the evapotranspiration rate of the reference crop,with the knowledge of the most important factor the simulation error will be reduced. Because of the differences among mathematical structure and underlying assumption of indirect reference crop evapotranspiration estimation methods, behavior of the response variable to changes in climatic parameters may become inconsistent. Therefore, it is mandatory to analyze the sensitivity as well as determining the influence of meteorological factors on reference crop evapotranspiration. In this study, the sensitivity of Penman-Monteith, Irmak, Copais and Valiantzas methods to changes in meteorological factors including maximum and minimum daily temperature, maximum and minimum relative humidity and short-wave radiation was analyzed in the research greenhouse of the College of Agriculture and Natural Resources of the University of Tehran, located in Karaj, Iran. Sensitivity coefficients were calculated by changing meteorological factors in the range of [20,-20] percent with 5% intervals. Results showed that in all methods, the internal radiation was the most influential variable in determining the reference crop evapotranspiration under greenhouse conditions. The obtained sensitivity coefficient for this variable in Penman-Monteith, Irmak, Copais and Valiantzas methods was equal to 0. 78, 0. 71, 0. 68 and 0. 63, respectively. In contrast, the least important climatic variable was the minimum humidity in Penman-Monteith, Copais and Valiantzas methods and the minimum temperature in Irmak method. The results also showed that Penman-Monteith is the most sensitive method to changes in meteorological factors. As a result, in case of using of Penman-Monteith method for reference crop evapotranspiration estimation in greenhouse conditions, ensuring the correct operation of measuring instruments and their accuracy is essential.

Spring vetch in single and mixed crops forms a green mass in various meteorological conditions and is a member of the green conveyor. It is widely used in intermediate crops (mowing, repeated, stubble). Due to the fact that pure crops of spring vetch are lodged, oats, spring wheat, barley, etc. are used as support crops. Most of the zoned varieties of the universal grain type have medium-sized seeds and are distinguished by high grain and green mass productivity. In variety testing of spring vetch of three varieties belonging to different groups by seed size, it is of interest to use them. Small-seed varieties of spring vetch are universal, while large-seed grain forage varieties. The search for varieties that meet high requirements for tolerance, field germination and survival in joint crops is an urgent task.

Background: The prevalence of Acute Myocardial Infarction (AMI) varies from region to region caused by seasonal climate changes and temperature variation. This study aimed to assess the relationship between changing meteorological conditions and incidence of AMI in Iran. Methods: This retrospective prevalence study was based on medical records of the heart center of Mazandaran Province on all patients diagnosed with AMI in Mazandaran, northern Iran between 2013 and 2015. Patients’ sex and the day, month, year and time of hospital admission were extracted from patients’ records. Moreover, the meteorological reports were gathered. Results: A statistically significant difference was found between the distributions of AMI cases across 12 months of the year (P < 0. 01). Fuzzy clustering analysis using 16 different climatic variables showed that March, April, and May were in the same cluster together. The other 9 months were in different clusters. Conclusion: Significant increase in AMI was seen in March, April and May (cold to hot weather).

This work investigated the connection between O3 and other pollutants and meteorological conditions during a smog episode in Delhi. Ozone concentrations varied from site to site (150~269µg/m3). A significant negative correlation has been observed between O3 and its precursor gases. Wind speed showed a positive correlation, but high wind usually dilutes the pollutant concentrations. Thus, a positive correlation with wind speed represents ozone transport from other locations to observational sites. The high ratio of PM2.5 to PM10 indicates a predominance of human involvement. Toluene and benzene ratios(T/B) are estimated to understand the nature of emission sources and the lifetime of pollution. The analysis of the benzene and toluene fractions indicates anthropogenic air masses' dominance. Very high T/B values at several sites indicated that benzene was emitted from vehicular emission while toluene was from point sources. Ozone formation potential analysis showed that toluene and p-xylene are the prime contributors to ozone.