Background:The mesoscale circulation over Kuwait is an important influence on changes in surface temperatures and soil temperatures.Introduction:This paper presents two common summertime atmospheric features over Kuwait linking wind circulation to soil temperatures.Methods:In this study, we use the European Centre for Medium-range Weather Forecasts ECMWF reanalysis ERA-Interim dataset to investigate effects of the synoptic scale and mesoscale circulations.Results:The results show that a large-scale pressure gradient in summer typically leads to northerly winds over Kuwait, while a weak synoptic-scale pressure gradient leads to light easterly humid winds from the Persian Gulf, consistent with a mesoscale circulation.Conclusions:The results demonstrate the significance of wind circulations in driving the Soil Temperature (SOILT). Using the Era-Interim/Land reanalysis dataset for August 2015 over Kuwait, the average SOILT on days of sea breeze is higher than the average SOILT on days dominated by a synoptic-scale pressure gradient.
Introduction:Changes in climate have impacts on natural and human systems on all continents and across the oceans. Most countries, including the UAE, are expected to experience a huge impact of climate change, due to the undergoing rapid growth and huge urban developments.Materials & Methods:Representative Concentration Pathways, or RCPs, represent the latest generation of scenarios that are used as potential inputs into climate models to show imposed greenhouse-gas concentration pathways during the 21stcentury. Four emission scenarios have been used for climate research; namely RCP 2.6, RCP 4.5 and RCP 6 and RCP 8.5. RCP 4.5 and RCP 8.5 are used. The aims of this study are to assess different RCPs and their appropriateness to predict temperatures and rainfall and to study the effect of climate change on three different cities in the UAE.Results & Conclusion:The results show a strong correlation between the present TmaxvsTmax 2020, Tmax 2040, Tmax 2060, Tmax 2080 and Tmax 2095 for both RCP4.5 and RCP8.5. This means that maximum temperatures are going to increase in the coming years based on the predictions according to the different scenarios using MarksimGCMR.Precipitation projections shows greater variation than temperature. In this paper the amount of increase in temperatures and precipitation change is shown for the end of the current century.
Objective: The diurnal variations of several ionospheric characteristics during the Space Weather Events of 4-10 September 2017, for Chilean latitudes, will be reported. Materials and Methods: Observations were made using a recently installed ionosonde at the Universidad de La Serena field station (29°52'S; 71°15’W). Also, reported is the total electron content determined using the upgraded Chilean network of dual-frequency Global Navigation Satellite Systems (GNSS) receivers. Results: Sudden ionospheric disturbances are described in terms of the minimum reflection frequency determined from ionosonde records. An attempt to derive the extent of the effect on high frequency propagation paths in the region is made using simultaneous ionosonde observations at other locations. The geomagnetic storm ionospheric effects are discussed in detail using the observed diurnal variation of maximum electron concentration (NmF2), virtual height of the F-region (h’F/F2) and Total Electron Content (TEC). These are complemented with the time-latitude variation of TEC for the 70°W meridian. Conclusion: It is found that large increases of NmF2, h’F/F2 and TEC observed during 8 September 2017 storm are well described in terms of the evolution of the Equatorial Ionospheric Anomaly (EIA) over the same time interval. Known physical mechanisms are suggested to explain most of the observations.
Background:Estimation of tropospheric radio refractivity is significant in the planning and design of terrestrial communication links.Methods:In this study, the monthly average daily atmospheric pressure, relative humidity and temperature data obtained from the National Aeronautics and Space Administration (NASA) during the period of twenty two years (July 1983 - June 2005) for Osogbo (Latitude 7.470N, Longitude 4.290E, and 302.0 m above sea level) were used to estimate the monthly tropospheric radio refractivity. The monthly average daily global solar radiation with other meteorological parameters was used to developed one, two, three and four variable correlation(s) tropospheric radio refractivity models for the location. The accuracy of the proposed models are validated using statistical indicator of coefficient of determination (R2), Mean Bias Error (MBE), Root Mean Square Error (RMSE), Mean Percentage Error (MPE), Nash - Sutcliffe Equation (NSE) and Index of Agreement (IA).Results:In each case one empirical model was recommended based on their exceptional performances after ranking, except for the two variation correlations with two empirical models. The recommended models were further subjected to ranking from which the three variable correlations model that relates the radio refractivity with the absolute temperature, relative humidity and global solar radiation was found more suitable for estimating tropospheric radio refractivity for Osogbo with R2= 100.0%, MBE = -0.2913 N-units, RMSE = 0.3869 N-units, MPE = 0.0811%, NSE = 99.9999% and IA = 100.00%.Conclusion:The newly developed recommended models (Equations 16c, 17d, 17f, 18d and 19) can be used for estimating daily and monthly values of tropospheric radio refractivity with higher accuracy and has good compliance to highly varying climatic conditions for Osogbo and regions of similar climatic information.
Some weather extremes can be the result of atmospheric blocking, which can be responsible for the stagnation of weather patterns. These large-scale quasi-stationary mid-latitude flow regimes can result in significant temperature and precipitation anomalies in the regions that the blocking event impacts. The ability to predict periods of anomalous weather conditions due to atmospheric blocking is a major problem for medium-range forecasting. Analyzing the NCEP Ensemble 500-mb pressure heights (240 h) ten-day forecasts, and using the University of Missouri blocking archive to identify blocking event, the forecasted duration and intensity of model blocking events are compared to observed blocks. Comparing these differences using four case studies occurring over a one-year period across the Northern Hemisphere has shown the continued need for improvement of the duration and intensity of blocking events. Additionally, a comparison of the block intensity to a diagnostic known as the Integrated Regional Enstrophy (IRE) was performed in order to determine if there is a correlation between these quantities. Having a better understanding of knowing how long each block will last and their associated anomalies can help society prepare for the damage they can cause. Simulating and identifying blocks correctly is important in improving forecast issues.
Introduction:Large Eddy Simulation (LES) modelers must begin to answer the question of how to better incorporate large datasets into simulations. This question is important because, at a given location, the diurnal, seasonal, and day-to-day variations of atmospheric stability have significant consequences for the power generated by wind turbines. The following study provides a methodology to obtain discrete values of surface flux, inversion height and geostrophic wind for LES using field data over multiple diurnal cycles (averaged over a month) at 12 Local Time (LT) (during the convective ABL). The methodology will allow the discrete LES to quantify the day-to-day variations over multiple diurnal cycles.Methods:The study tests the hypothesis that LES can capture the mean velocity and TKE profiles from the averaged variations in surface heat flux at 12 LT measured in the field (mean, +1 standard deviation, and -1 standard deviation). The discrete LES from the mean, +1 standard deviation, and -1 standard deviation surface heat flux represent the variations in the ABL due to the day-to-day variations in surface heat flux. The method calculates the surface heat flux for the NREL NWTC M5 dataset. The field data were used to generate Probability Density Functions (PDFs) of surface heat flux for the January and July 12 LT. The PDFs are used to select the surface heat fluxes as inputs into the discrete LES.Results / Conclusion:A correlation function between the surface heat flux and the boundary layer height was determined to select the initial inversion height, and the geostrophic departure function was used to determine the geostrophic wind for each surface heat flux. The LES profiles matched the averaged velocity profiles from the field data to 4% and the averaged TKE profiles to 6% and, therefore, validated the methodology. The method allows for further quantification of day-to-day stability variations using LES.
Introduction/ Methods: The current study has compared the fluctuations of atmospheric precipitable water over Iran during three periods of 1948 – 1957, 1958 – 1978, and 1979 – 2012 using upper-air reanalyzed data from NCEP/NCAR. Results: The results indicated that, in all the three periods, average distribution and coefficient of spatial variation decreased with altitude. In contrast, there was a positive relationship between coefficient of spatial variation and altitude. The results of trend analysis showed that atmospheric precipitable water of Iran calculated using the upper-air reanalyzed data by NCEP/NCAR experienced various fluctuations during the three periods of 1948 – 1957, 1958 – 1978, and 1979 – 2012. The increase of the precipitable water during the first period was not significant at the level of 95%. The increase of the precipitable water during the second period was significant at the level of 95% just in 25% of the regions. In contrast to the second period, 70% of the country’s area followed a declining trend. However, this decreasing trend was not significant at the level of 95%, either. Conclusion: The results of Alexandersson statistical method showed that the biggest shift in the average of precipitable water happened during the third period. Overall, variations in the precipitable water over Iran in the past ~60 years are not within the uncertainty of the reanalysis data and are therefore clearly discernible.
Objective:This research is dedicated to the study of the feasibility of surface wind downscaling from 925 or 850 hPa winds according to synoptic class, season and hour.Methods:Two aspects are examined: low tropospheric wind veering and wind speed correlation and verification of the ERA-Interim analysis wind by comparison to radiosonde data at Beit Dagan, a station on the Israeli coast.Results:Relatively small (< 60°) cross angles between the 1000 hPa wind vector and the 925 hPa or 850 hPa wind vector at 12Z and high correlation (0.6-0.8) between the wind speed at the two levels were found only under winter lows. Relatively small cross angles and small wind speed correlation were found under highs to the west and Persian troughs.The verification of ERA-Interim analysis in comparison with radiosonde data has shown good prediction of wind direction at 12Z at 1000, 925 and 850 hPa levels (RMSE 20°-60°) and lower prediction quality at 1000 hPa at 0Z (RMSE 60°-90°). The analysis under-predicts the wind speed, especially at 1000 hPa. The wind speed RMSE is 1-2 m/s, except for winter lows with 2-3 m/s RMSE at 0Z, 12Z at all levels.Conclusion:Inference of surface wind may be possible at 12Z from 925 or 825 hPa winds under winter lows. Inference of wind direction from 925 hPa winds may be possible under highs to the west and Persian troughs. Wind speed should be inferred by interpolation, according to historical data of measurements or high resolution model.
Background:The 26 December 2003 snowstorm was a rare and long-lived weather system that affected east Idaho. Light snow began falling Christmas night, became steadier and heavier during the next day, and tapered off during the morning on the 27th. Snowfall estimates of 20.3-38.1 cm (8.0-15.0 in) were observed over a 24-hour period on 26 December 2003 in the lower part of the Snake River Plain, paralyzing local communities and transportation centers with snowdrifts and poor visibilities.Methods:The Weather Research and Forecasting Unified Environmental Modeling System was used to conduct a sensitivity study of five precipitation microphysics schemes at two grid scales during the event.Results:A comparison of the model accumulated total grid scale precipitation at 12-km and 4-km scales with the observed precipitation at several stations in the lower plain, indicated small negative biases (underprediction) in all of the schemes. The Purdue-Lin and Weather Research and Forecasting Double-Moment 6-Class microphysics schemes contained the smallest root mean squared errors.Conclusion:The Purdue-Lin and Weather Research and Forecasting Double-Moment 6-Class schemes provided several insights into the dynamics of the snowstorm. A topographic convergence zone, seeder-feeder mechanism, and convective instability were major factors contributing to the heavy snowfall in the lower plain.
Aim:This study aimed to investigate the impact of using Global Positioning System Radio Occultation (GPS RO) sounding data (i.e., Constellation Observing System for Meteorology, Ionosphere, and Climate; COSMIC) for Tropical Cyclogenesis (TC-genesis) research.Methods:The Weather Research and Forecasting (WRF-ARW) model and the WRF data assimilation system (i.e., WRF 3DVAR) were employed to simulate Tropical Depression- 8 (TD8) 2006. A noteworthy feature about TD8-genesis was that Saharan dust outbreak was also observed during this period, which made this event more sophisticated. The time frame to be focused on was from 1200 UTC September 09 to 1200 UTC September 12, 2006. The level 2 wetPrf COSMIC data was adopted in this research. A 72-hour integration wasperformed with initial and time-dependent lateral boundary conditions derived from the NCEP final analysis data (FNL). A 2-domain nested simulation was configured with 30 km, and10 km horizontal resolutions, respectively.Results:Simulation results from all the experiments performed with different RO soundings combination showed that the RO sounding 8 has the greatest significant impact on TD8 simulation.Conclusion:Elevation, time, and location are the parameters that made RO sounding 8 the most treasured sounding to analyze TD8.
Background: In February 2017, some buildings of La Pineda (Catalonia, NE Spain) a rather small town, located near to the Tarragona harbor, were affected by a contamination episode that dirtied external walls, windows, doors and floors of these buildings with a black dust. This study was aimed at assessing the origin of the black dust appeared in the buildings. Methods: Black dust samples were collected in the railings of balconies, windows, and exterior doors of two buildings in La Pineda, as well as in the ground of the breakwater of the Tarragona harbor, at few meters from the open air coal storage area. Elemental analysis of the black dust (C, N, H and S) was performed. A daily sample of PM10 was also collected and analyzed for five consecutive days. Results: The total carbon content of the collected dust was 25.8%, 29.4% and 33.9% in the two buildings of La Pineda and the breakwater, respectively. In turn, the contribution of carbon from carbonates was 0.0%, 1.3% and 5.1%, in the samples of the two buildings and the breakwater, respectively. PM10 showed levels between 18 and 39 µg/m3, with mean and median levels of 29 µg/m3. Conclusion: The elemental analysis indicated that the two black dust samples collected in the two buildings of La Pineda were similar to the sample collected at the breakwater of the port of Tarragona, showing a common origin: The bulk coal storage area of Tarragona harbor. Because information on the human health risks derived from the important activities conducted in the port of Tarragona is currently non-existent, an exhaustive assessment of all pollutants involved in the activities of the port is strongly recommended.
Background:In this work the disturbances of the near surface electric field are investigated, which are attributed to different types of atmospheric discharges: intracloud or cloud-to-ground.Method:The patterns of the lightning occurrences are discussed as measured by the network of the electric field mills located at the stations of Cosmic Ray Division of Yerevan Physics Institute. Discharges make changes in the near surface electric field, which can be separated into two groups. The differences of those two groups and shapes of the recovery curves are discussed using the data from electric field mills network for a stormy day on May 23, 2015.Conclusion:The results presented in this work show that magnitudes of field changes from one of the groups are larger and have shorter duration compared to another one. Recovery curves of the near surface electric field produced by lightning flashes also have a power-law or a linear dependence besides exponential shape.
The Sun as climate driver is repeatedly discussed in the literature but proofs are often weak. In order to elucidate the solar influence, we have used a large number of temperature proxies worldwide to construct a global temperature mean G7 over the last 2000 years. The Fourier spectrum of G7 shows the strongest components as ~1000-, ~460-, and ~190 - year periods whereas other cycles of the individual proxies are considerably weaker. The G7 temperature extrema coincide with the Roman, medieval, and present optima as well as the well-known minimum of AD 1450 during the Little Ice Age. We have constructed by reverse Fourier transform a representation of G7 using only these three sine functions, which shows a remarkable Pearson correlation of 0.84 with the 31-year running average of G7. The three cycles are also found dominant in the production rates of the solar-induced cosmogenic nuclides14C and10Be, most strongly in the ~190 - year period being known as the De Vries/Suess cycle. By wavelet analysis, a new proof has been provided that at least the ~190-year climate cycle has a solar origin.
Background:Nitric oxide concentration in the upper atmosphere is known to be highly dependent on the solar activity. It can be transported to the stratosphere by the atmospheric circulation. In the stratosphere it is responsible for the destruction of ozone and consequently stratospheric heating rates are affected. This is one of the mechanisms by which solar variability has been suspected to drive variability in the energetic budget of the Earth climate. Therefore, it is essential to know every physical and chemical processes leading to the production or to a destruction of nitric oxide.Aim:The aim of this work is to calculate the production rate of NO+and some of the NO electronic states created by electron impact on NO at night in the auroral zone using an electron transport code.Conclusion:We study this variability under different precipitation conditions and taking into account the variability of the neutral atmosphere with the geomagnetic and solar activity. We find that the energetic electron precipitation has a very small effect on the absolute value of the NO+and NO* production rates. In order to help further research to consider the effect of NO+and NO*, we provide a table of all the production rates in a medium solar and geomagnetic activity case.
Background:Evidence has accumulated in recent years regarding the scope of local and global climate changes attributed to exacerbating anthropogenic factors such as accelerating population growth, urbanization, industrialization, traffic and energy use. Remote space monitoring, unlike ground-based measurements, has the advantage of providing global coverage on a daily basis.Methods:MODIS (Moderate Resolution Imaging Spectroradiometer) Aqua and Terra 1°×1° spatial resolution as well as the 1 km higher resolution of Aqua-MODIS were investigated for a global overview of megacities temperature variations, as well as the recent trends of the 10 largest Monsoon Asian megacities.Results:The average Land Surface Temperature (LST) cross-sections of the 10 Asian megacities were examined for June-August 2002-2014. Temperature variations fit a spatial bell-shaped curve, with a pronounced maximum over the city center. Nighttime data indicated sharp LST decreases with distance from the city center, particularly in the coldest cities, those of Tokyo, Seoul, Osaka and Beijing.Conclusion:Daytime latitudinal (E-W) and longitudinal (N-S) Surface Urban Heat Islands (SUHI) have steeper gradients than for nighttime data. During daytime, the SUHI gradients are largest in Tokyo, Seoul, Osaka and Beijing with values reaching 15oC followed by the cities of Shanghai and Guangzhou with ~11oC, and Karachi with ~5oC SUHI. Nighttime SUHIs were more moderate, 4-6oC in Tokyo, Seoul ~5oC, Osaka 5-7oC and Beijing ~7oC. Only in the three largest megacities,i.e., Tokyo, Guangzhou and Shanghai, did the nighttime LST trends decline.
Background:The varied topographical features of the Indian region are responsible for variation in distribution of rainfall over different parts of the country. More than 80% of the country’s rainfall is received during the monsoon season. Researchers noted that there is change in distribution of this monsoon rainfall associated with climate change and global warming. This changing pattern in rainfall can be investigated by seasonality index (SI) of rainfall. Such studies are essential to identify the changes in runoff, infiltration, surface and groundwater management, agricultural planning,etc.Method:The variation in seasonality in rainfall over the Indian region is examined using monthly rainfall values for the period 1951 to 2015 of 34 meteorological sub-divisions excluding two Sea Islands. A seasonality index (SI) of a monthly rainfall is computed on monthly, seasonal (June to September) and annual scale. It is observed that seasonality index of rainfall of 34 sub-divisions for all months are in the range 0.37 (Jammu & Kashmir) to 1.56 (Saurashtra Kutch & Diu).Results:The results show that rainfall is markedly seasonal with a long dry season and most rainfall in less than three months. Most of the rainfall occurs in monsoon months. The seasonality index for monsoon season is computed and it varies from 0.19 (Nagaland, Manipur, Mizoram,Tripura) to 0.59 (Saurashtra Kutch & Diu) resulting in rainfall spread throughout the year, but with a definite wetter season.Conclusion:Trends of this index through the 65-year period are identified and indicate that seasonality is increasing in Uttaranchal, Himachal Pradesh, Gujarat Region-Dadra & Nagar Haveli; Saurashtra-Kutch & Diu, Konkan & Goa, Madhya Maharashtra, Marathwada, Chattisgarh, Tamilnadu & Pondicherry. The analysis clearly showed the climate change impact on northwest sub-divisions of the country showing increase in SI values leading to dryness during the monsoon season. The negative trend in SI values was observed in Sub- Himalayan West Bengal, Haryana-Delhi-Chandigarh, Punjab, Jammu & Kashmir, West and east Rajasthan, coastal Andhra Pradesh showing increasing wetness for an already wet months although rainfall occurs in a very short period of just a month or two.
Background: Simultaneous measurements of air temperature were carried out using automatic weather stations at 14 tropical locations in Nigeria. Diurnal variations were derived from the 5-minute update cycle initial data for the years ranging between 2007 and 2013. The temperature trends in Nigeria revealed a continuous variability that is seasonally dependent within any particular year considered. Method: The analysis was carried out using available data from the network and the results are presented with a focus to characterize the temperature variations at different locations in the country using the mean, maximum and minimum temperatures from the north which is arid in nature to the south, which is a tropical monsoon climate type and a coastal region. Result: In overall, temperature variations in Nigeria were observed to have higher values in the far north, attributed to the influence of Sahara Desert, which has less cloud cover and therefore is more transparent to solar irradiance and lowers values in the south, where there are more cloud cover and abundant vegetation. Conclusion: Measured maximum and minimum temperatures in Nigeria are respectively 43.1°C at Yola (north-east part of Nigeria) and 10.2°C for Jos (north-central part of Nigeria). The least temperature variations were recorded for stations in the southern part of the country, while the largest variations were recorded in the north-central region of the country.
An investigation of the response of the mid-high, mid and low latitude critical frequency foF2 to the geomagnetic storm of 15 July 2000 is made. Ground-based hourly foF2 values (proportional to square root of peak electron density of F2-layer) from four chains of ionospheric stations located in the geographic longitude ranges 10°W–35°E, 60°E–120°E, 130°E–170°E, 250°E–295°E are used. Relative deviations of foF2 are considered. The main ionospheric effects for the considered storm are: long-duration negative disturbances at mid-high latitudes in summer hemisphere in sectors where the storm onset occurred in the afternoon/night-time hours; short-duration positive disturbances in the summer hemisphere at mid-high latitudes in the pre-sunset hours during the end of main phase-first stage of the recovery; small and irregular negative disturbances in the low latitude winter hemisphere which predominate during the main phase and first part of the recovery, and positive disturbances in both hemispheres at mid-high and mid latitudes prior to the storm onset irrespective of the local time. In addition, the validity of some physical mechanisms proposed to explain the F2 region behaviour during disturbed conditions is considered.
Background: Low-frequency atmospheric waves with gravity modes were recorded within 6.5 hours and 4.7 hours after two recent Chilean megathrust events, the 2010 Maule (Mw = 8.8), and 2014 Iquique (Mw = 8.2) earthquakes, respectively, at several microbarograph stations of the International Monitoring System (IMS) in South America and its surrounding regions. Method: Their apparent phase velocity up to the epicentral distances of 7,404 km and 6,481 km was found to be around 319 m/s and 337 m/s, respectively for the gravity modes after the two earthquakes. We tried to construct synthetic waveforms to be recorded at some of these microbarograph stations, incorporating various seismic source characteristics of the two earthquakes, and also a standard sound velocity structure up to a height of 220 km above the ground surface. The comparison appears to show some agreement between the observed and synthetic waveforms at least for the first 22 min for appropriate combinations of these source parameters. Results: The results indicate that the observed atmospheric gravity waves at the initial stage appear to have actually been excited at the source region of these megathrust earthquakes. Conclusion: The average rise time of vertical tectonic movement at the source region, which is estimated to be from the observed gravity waves, appears to be in the range between 2 and 3 min.
Background:This paper investigates sensitivity of bulk microphysical parameterization (BMP) schemes within the Weather Research and Forecasting (WRF) model to simulate a convective storm that generally evolves during pre-monsoon season (March – May) across the foothills of the Himalayas.Method:Four mixed-phase BMP schemes (Morrison, Lin, WDM6, and WSM6), which are parameterized with an increasing complexity from single to double moments of particle distribution to represent cloud processes, are used with an explicit convection permitting grid resolution (3 km x 3 km). Experiments are set up to simulate a convective storm that occurred in the late afternoon of 18thMay 2011 and compared with i) Satellite-based tropical rainfall measuring mission (TRMM) 3B42 v7 data, and ii) Ground-based observations at Nagarkot (27.7°N, 85.5°E), Nepal.Result:Our results show that the simulated storm characteristics are not overly sensitive to the chosen BMP schemes. In general, all the BMP schemes produce similar rainfall characteristics and compares reasonably well with the observations across Siwalik Hills and Middle Mountains, which act as a topographic barrier to low level circulations and receive more rain. The schemes, however, show negative bias across central Nepal including the Kathmandu Valley, albeit the magnitude and spatial distribution of bias are different between the schemes. In contrast, upper level total water condensate and cloud fraction show a strong sensitivity to the BMP schemes.Conclusion:Overall, the Morrison scheme, in addition to warm clouds which also predict double moment distribution of all hydrometeors in the cold-cloud processes, a dominant cloud forming process in the Himalayas, accurately represents the mechanism and outperforms the simplified schemes based on root mean square error (RMSE) analysis.
