For a synoptic analysis of high polluted days in 13 and 14 November 2007, a combinatorial synoptic analysis was used. From methodology prospect, the present study has utilized the "circular environment" synoptic approach and with respect to the restrictions on very high-polluted days in Mashhad city, the subjective synoptic analysis used for data processing and analyzing the prevailing atmospheric conditions.
In the present research, four sets of the data, including the pollution data recorded at the stations monitoring air pollution, digital atmospheric data, data of upper air stations and the outputs of HYSPLIT model were utilized. The data on air pollution obtained from the Department of Environment Protection of Khorasan Razavi were related to Wahdat station located in the center of Mashhad city. The pollutants include CO, NO2, SO2, ozone, and particulate matter (PM10( prepared and processed on a daily scale for a 7-year statistical period (2005-2012). When studying the quality of air pollution over Mashhad city, it is necessary to indicate that Mashhad city had only one station monitoring air pollution (Wahdat station) until 2010 and unfortunately, out of 10 present stations for monitoring the air pollution, only Wahdat station was involved a suitable statistical period duration to be studied. Accordingly, the present study has been conducted only by using the pollution data recorded in Wahdat station and utilizing the data of other stations ignored due to the shortness of statistical period duration. The reanalyzed data of the National Centers for Atmospheric Prediction (NCEP) and the National Center for Atmospheric Research (NCAR) with a horizontal separation 2.5 × 2.5 were used in order to study the atmospheric conditions. The atmospheric conditions include the sea level pressure, geo-potential height, vertical velocity, and orbit wind (u) & meridian wind (v) components on different atmospheric levels from the past 48 hours and in a 6-hour interval. In addition, upper air data about Mashhad station (Mashhad airport) were used on a similar period. Upper air data have been obtained from the website of Wyoming university (http://weather.uwyo.edu/upperair/sounding.html) on under study days, including air temperature, dew point, direction, wind intensity and the atmospheric stability and instability conditions (based on Skew-T Curves – logP). These data are only available on Zero Greenwich hour. The outputs of the HYSPLIT model were also used as complementary data for tracing particulate matter in days 10 -15 in November. In this study, the HYSPLIT model, version 4.9 was used. In the present research, the role of regional atmospheric circulation and pressure patterns were investigated on a synoptic scale in very high-polluted days in November 2007 in Mashhad metropolitan. For this purpose, the mechanism dominated on occurring a very high-polluted period in this city was analyzed using a combinatorial method based on synoptic and thermodynamic analyses as well as tracing particulate matter. The results of studies involve the following findings: the days 13 and 14 November 2007 (22 and 23 Aban, 1386) show the highest concentration rates among the polluted days in Mashhad city. The findings of the research show that the synoptic pattern dominated the very high polluted period (13 and 14 November 2007) is a migrant high-pressure pattern. Accordingly, it may be concluded that the incidence of serious pollutions in Mashhad is initially the result of interacting local conditions with air circulation on a regional scale and then the other local factors. In the other words, Mashhad city would experience very high-polluted days only when regional atmospheric circulation provides suitable conditions to increase the concentration of pollutants. What is obvious is that in the winter season the serious pollutions occurred in Mashhad city are mainly as the results of prevailing extra-tropical systems (migrant anticyclone). Studying subjective synoptic analysis, tracing the backtracking of particulate matter and the atmospheric thermodynamic conditions ( combinatorial synoptic analysis) have provided a deeper and more accurate understanding of the conditions prevailing in the occurrence of serious pollutions in the northeast of Iran. Studying the output of the HYSPLIT model indicates that the migrant stack system of western wave together with the subtropical stack would control the air circulation pattern on the northeast of Iran in 13 and 14 November 2007. Tracing the particulates shows an anticyclone system on the zone. Also, studying SKEW-T Curves related to the migrant high-pressure pattern revealed a different structure, so that the day 12 November 2007 faced with a radiation inversion along with an increased temperature, but on day 13 November 2007 an inversion from the sort of subsidence between the interval of level 850 to 700 hpa was appeared and also reached to higher than 700 hpa.
Sea surface temperature is one of the most effective physical parameters that affects the health of coral reefs communities.High frequency of the bleaching phenomenon has extensively occurred in the Persian Gulf in the recent years due to the increase in temperature and increased changes in the sea surface temperature (SST) resulting in great mortality in the coral communities. The aim of this research is to determinate a temperature threshold which may function as a warning for the incidence anticipation of this phenomenon. Data on the variation of the SST that has been taken from National Oceanic and Atmospheric Administration (NOAA). Information related to bleaching in the regions of the southern Persian Gulf was extracted from the published papers and reports. Each of these sources also has been extracted for a 35-year statistical course (1980-2015) and by the index of degree heating weeks (DHWs) determined for the same statistical course in this research for the assessment and anticipation of bleaching phenomenon. For reviewing of the work accuracy, Peirce Skill Score (PSS) technique was used to quantify the accuracy of previous and subsequent anticipations. According to the derived results, DHWs threshold for the study region was determined to be 7.13. the threshold 7.13 for DHW is suggested as a caution threshold for bleaching incidence in southern regions of the Persian Gulf that is whenever the values of weekly positive temperature DHW show number 7.13 and higher, there is an expectation of bleaching phenomenon incidence of corals for these regions. And the score of PSS= 0.72 derived from the amounts of H= 7/8= 0.87 for the Hit rate and F= 4/26= 0.15 for the False alarm rate of the bleaching was obtained for the southern regions of Persian Gulf and study region. In northern regions of the Persian Gulf the threshold 5.3 for DHW is suggested as a caution threshold for bleaching incidence. The rate of pss = 0.62 derived from the amounts of (3/4 = 0.75) for the Hit rate and ( 3/23 = 0.13) for the False alarm rate of the bleaching was obtained for the northern regions of Persian Gulf and study region. Difference in DHWs values of the south and north of Persian Gulf shows more resistance of the corals of south Persian Gulf against DHW changes and SST anomalies. Also the amounts of DHW alongside SST can help more completely to the anticipation of bleaching phenomenon.
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