دراسة الاشعاع طويل الموجة الخارج فوق العراق باستعمال بيانات AIRS == Study of Outgoing Longwave Radiation Over Iraq Using AIRS Data
Author name:
صفاء عبد الرزاق عبد الحسين
Supervisor name:
علي محمد الصالحي
General topic:
Meteorology
Specific topic:
Atmospheric Sciences
Degree:
Master
University:
Mustansiriyah University - College Of Science - Department Of Atmospheric Sciences
Language:
English
University location:
Baghdad
First pages:
32T52 - p.pdf
Abstract:
Outgoing longwave radiation (OLR) is a thermal energy represents total upward radiation from the Earth - Atmosphere system towards space. Clouds and greenhouses gases trapped and absorb certain wavelengths of OLR and radiated back towards the Earth, this led to adding an amount of heat to the atmosphere. Variation in OLR values would be influenced Earth’s climate system by increasing or decreasing the average temperature of the Earth's surface. The present thesis involves analysis the spatiotemporal distribution of the outgoing longwave radiation (OLR) and developing an OLR estimation models. Dataset acquired from polar orbit satellite Aqua and its instrument the Atmospheric Infrared Sounder (AIRS). The study was carried out using data collected from January 2003 to December 2016 which covered a region [W : 37.5, S : 28.5, E : 49.5, N : 38.5] in a grid of resolution of 1º×1º. The 13 - years data from 2003 to 2015 were used for climatology and for establishing relationships in the developed models, multiple linear regression (MLR) and Artificial Neural Network (ANN)because the suitability of the technique to provide estimates, while the data of the year 2016 was employed to investigate the estimation capacities of these models of monthly - average OLR value in Iraq. The spatiotemporal distribution of monthly averaged values of OLR for 13 years period showed that Winter season have the minimum average values, about (270 15.8) Wm - 2. Start from Spring season OLR levels become increasingly intense and reach (306 16.2) Wm - 2. Summer season became more intense when compared to previous seasons, specifically over the southern parts of Iraq and dominate the highest OLR overall observed average values. These values reached (351 16.2), (360 14.5), (355 12.9) Wm - 2 for June, July and August respectively. As Autumn season start, the reduction of overall average OLR values start. The minimum average values reached in November with a (283.6 12.3) Wm - 2. The results also showed a zonally relationship between OLR and latitude. The spatial variance of OLR values were indicates an indirect zonally relation between OLR and latitude.Different observed meteorological parameters, including (Surface temperature (ST), Relative humidity (RH), and Cloud fraction (CF)) were offered as the input variables for modeling ANN and MLR to get OLR values. For the entire period, these three meteorological parameters were highly correlated (R= 0.980) with measured OLR. Furthermore, satellite data were used in three different locations over Iraq (Mosul, Baghdad and Basrah). Estimations of OLR values were evaluated by using several statistical bases. Comparisons among the three selected cities in test data (the year 2016) showed close agreement between the estimated OLR and measured OLR from AIRS. Mosul city at the north of the study area showed the best statistical performance indicators with the lowest root mean square error (RMSE) of (4.4966 and 1.3853) and highest correlation coefficient (R) of (0.9929 and 0.9993) for the two models (MLR and ANN) respectively, indicating model's efficiency and accuracy. Statistical analysis in term of β (regression constant) showed that surface temperature (1.823 to 2.311) tended to contribute significantly to high OLR values.The estimated results showed a satisfying performance for the ANN model when compared to the MLR model. These results obviously indicate the advantage of using the satellite AIRS data and both of MLR and ANN models to investigate the impact of the atmospheric meteorological parameters on OLR values on cities and country. Finally, the MLR model is used to map the estimated monthly average of OLR over Iraq.
