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Sayad T.A.,Al - Azhar University of Egypt | El-Hussainy F.M.,Al - Azhar University of Egypt | Amin I.M.,Egyptian Meteorological Authority
International Journal of Meteorology | Year: 2010

In this paper three methods of the multiple regression from temperature, water vapour pressure and cloud fraction are used to estimate the downward long-wave radiation at surface of the earth (DLWRS) over Cairo and Aswan, Egypt using statistical model (lnstat). Firstly Brunt equation is improved by using the local parameters over Cairo and Aswan to decrease the Mean Absolute Error (MAE) to be 6.5 % for Cairo and 8.11 % for Aswan compared with the corresponding error from original Brunt equation (11.1 % for Cairo and 23.5 % for Aswan). Secondly adding the cloud fraction to the temperature and water vapour pressure in the multiple regressions is noticed to reduce MAE to be 4.85 % for Cairo and 4.92 % for Aswan. Finály cloudy days are separated from clear sky days over Cairo and Aswan. The errors are improved over Aswan more than Cairo to be 3.7 %, 3.4 % for Aswan and 4.28 %, 4.27 % for Cairo respectively. © THE INTERNATIONAL JOURNAL OF METEOROLOGY. Source


Wahab M.A.,Cairo University | El-Metwally M.,Suez Canal University | Hassan R.,Egyptian Meteorological Authority | Lefevre M.,MINES ParisTech | And 2 more authors.
International Journal of Remote Sensing | Year: 2010

Two databases of solar surface irradiance (SSI) derived from satellites were compared to ground measurements in Algeria, Egypt, Libya and Tunisia. We found that it was possible to accurately derive the SSI from geostationary meteorological satellites, even with a coarse spatial resolution. The two databases HelioClim-1 (HC1) and SSE exhibited similar and good performances. The bias was generally lower for SSE than for HC1; however, HC1 exhibited a smaller scattering of data compared to ground measurements (smaller standard deviation) than the SSE, allowing better performance when mapping the long-term variations in SSI. The long-term variations in SSI from 1985 to 2005 show that these four countries as a whole experienced dimming. Detailed analyses of the range of dimming at sites with long-term records and of its spatial distribution were performed. We found that the analysis of SSI from HC1 supports the findings for the individual sites. Dimming may be explained by: (1) transportation of sand dust northwards from the Sahel, (2) an increase in urbanization, and (3) an increase in cloud cover and aerosol loading. © 2010 Taylor & Francis. Source


Steiner A.L.,University of Michigan | Tawfik A.B.,University of Michigan | Tawfik A.B.,Center for Ocean Land Atmosphere Studies | Shalaby A.,Egyptian Meteorological Authority | And 6 more authors.
Climate Research | Year: 2014

An integrated chemistry-climate model (RegCM4-CHEM) simulates present-day climate, ozone and tropospheric aerosols over Egypt with a focus on northern Africa and the Greater Cairo (GC) region. The densely populated GC region is known for its severe air quality issues driven by high levels of anthropogenic pollution in conjunction with natural sources such as dust, and agricultural burning events. We find that current global emission inventories underestimate key pollutants such as nitrogen oxides and anthropogenic aerosol species. In the GC region, average ground-based observations of the daily July maximum nitrogen dioxide (NO2) are 40 to 60 parts per billion by volume (ppbv) and are about 10 ppbv higher than modeled estimates, likely due to model grid cell resolution, improper boundary layer representation, and poor emissions inventories. Observed July daily maximum ozone concentrations range from 30 ppbv (winter) to 90 ppbv (summer). The model reproduces the seasonal cycle fairly well, but modeled July ozone is underestimated by approximately 10 ppbv and exhibits little interannual variability. For aerosols, springtime dust events dominate the seasonal aerosol cycle. The chemistry-climate model captures the springtime peak aerosol optical depth (AOD) of 0.7 to 1 but is slightly greater than satellite-derived AOD. Observed AOD decreases in the summer and increases again in the fall due to agricultural burning events in the Nile Delta; however, the model underestimates this observed AOD peak in fall, as standard emissions inventories underestimate the extent of this burning and the resulting aerosol emissions. Our comparison of modeled gas and particulate phase atmospheric chemistry in the GC region indicates that improved emissions inventories of mobile sources and other anthropogenic activities, specifically NOx and organic aerosols, are needed to improve air quality simulations in this region. © Inter-Research 2014. Source


Eissa Y.,Masdar Institute of Science and Technology | Eissa Y.,MINES ParisTech | Korany M.,Egyptian Meteorological Authority | Aoun Y.,MINES ParisTech | And 8 more authors.
Remote Sensing | Year: 2015

HelioClim-3 (HC3) is a database providing time series of the surface downwelling solar irradiance that are computed from images of the Meteosat satellites. This paper presents the validation results of the hourly global horizontal irradiance (GHI) and direct normal irradiance (DNI), i.e., beam irradiance at normal incidence, of versions four and five of HC3 at seven Egyptian sites. The validation is performed for all-sky conditions, as well as cloud-free conditions. Both versions of HC3 provide similar performances whatever the conditions. Another comparison is made with the estimates provided by the McClear database that is restricted to cloud-free conditions. All databases capture well the temporal variability of the GHI in all conditions, McClear being superior for cloud-free cases. In cloud-free conditions for the GHI, the relative root mean square error (RMSE) are fairly similar, ranging from 6% to 15%; both HC3 databases exhibit a smaller bias than McClear. McClear offers an overall better performance for the cloud-free DNI estimates. For all-sky conditions, the relative RMSE for GHI ranges from 10% to 22%, except one station, while, for the DNI, the results are not so good for the two stations with DNI measurements. © 2015 by the authors. Source


Korany M.,Egyptian Meteorological Authority | Boraiy M.,Port Said University | Eissa Y.,Masdar Institute of Science and Technology | Eissa Y.,MINES ParisTech | And 8 more authors.
Earth System Science Data | Year: 2016

A database containing the global and diffuse components of the surface solar hourly irradiation measured from 1 January 2004 to 31 December 2010 at eight stations of the Egyptian Meteorological Authority is presented. For three of these sites (Cairo, Aswan and El-Farafra), the direct component is also available. In addition, a series of meteorological variables including surface pressure, relative humidity, temperature, wind speed and direction is provided at the same hourly resolution at all stations. The details of the experimental sites and instruments used for the acquisition are given. Special attention is paid to the quality of the data and the procedure applied to flag suspicious or erroneous measurements is described in detail. Between 88 and 99% of the daytime measurements are validated by this quality control. Except at Barrani where the number is lower (13 500), between 20 000 and 29 000 measurements of global and diffuse hourly irradiation are available at all sites for the 7-year period. Similarly, from 9000 to 13 000 measurements of direct hourly irradiation values are provided for the three sites where this component is measured. With its high temporal resolution this consistent irradiation and meteorological database constitutes a reliable source to estimate the potential of solar energy in Egypt. It is also adapted to the study of high-frequency atmospheric processes such as the impact of aerosols on atmospheric radiative transfer. It is planned to update regularly the current 2004-2010 database, which has been placed on the PANGAEA repository (doi:10.1594/PANGAEA.848804) and contains the individual meteorological and irradiation data files of the eight stations. © Author(s) 2016. Source

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