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The spatial and temporal variations of aerosol optical depth at 550 nm (τ550) and Angstrom exponent derived from 470 and 660 nm (α470-660) over Nairobi (NAI), Skukuza (SKU) and Ilorin (ILO) Aerosol Robotic Network (AERONET) stations in sub-Saharan Africa, as recorded by Moderate Resolution Imaging Spectroradiometer (MODIS) satellites for fifteen years (2000-2015), were examined in relation to their climatologies and prediction. The MODIS measurements of τ550 and α470-660 from aqua (MYD04) and terra (MOD04) satellites were used in this study. Retrievals of τ550 for both satellites were validated with AERONET τ550 for the same period. The validation results showed that they compare favourably over the three stations, but MOD04 performed better than MYD04 data in NAI and ILO for τ550. This shows that the τ550 of NAI and ILO are best captured using the MOD04 data while that of SKU is best with MYD04. It was also discovered that MODIS underestimated AERONET τ550 data over NAI and SKU. The most polluted station is ILO while the least polluted one is NAI. Similarly, the station with the highest concentration of absorbing aerosols is NAI and the least was observed in ILO. The aerosol climatology shows that the most polluted months in NAI, SKU and ILO are October, June and March respectively. On the other hand, February, November and March has the highest amount of scattering aerosols in the atmosphere for NAI, SKU and ILO respectively. The highest amount of absorbing aerosols was found, respectively, in the months of June, June and August. The generated time series (TS) models are all good, though a general underestimation of the parameters by the models was also observed. Keywords: Aerosol optical depth, Angstrom exponent, MODIS, Time series, sub-Saharan Africa

Characteristic variation of ground heat flux and net radiation enhances the understanding of the significance of indicated trends of variability to everyday life and factors that might be responsible for such variations. This research work critically analyses some specific days with field data over grass-covered surface at Ile-Ife, Nigeria between ground heat flux and net radiation. For the field observations, an instrumented meteorological mast was set up at an experimental site (7°33’N, 4°35’E) located at Obafemi Awolowo University campus, Ile-Ife, Nigeria for a period of two weeks (31st May-14th June, 2013). The soil heat flux, net radiation and soil temperature from the soil heat flux plate; an all-wave net radiometer, and soil thermometer were recorded every 10 seconds and averaged over 2 minutes interval. The sampled data was stored in the data logger (Campbell Scientific, Model CR10X) storage module. After the removal of spurious measurement values (Quality Assurance and Quality Control), the data stored was further reduced to 30 minutes averages using the Microcal Origin (version 7.0) data analysis software. The results showed that the measured ground heat flux, HGM during the daytime increases until 1400 hrs with maximum value of about 136.86 Wm-2 and minimum value of about -72.87 Wm-2 at 0830 hrs (DOY 156). The measured net radiation, Rn value of 649.65 Wm-2 observed at 1400 hrs (DOY 156), represented the maximum value for the entire period of the study. -10.75 Wm-2 value observed at1800 hrs (DOY 154), represented the minimum value for the entire period of the study due to the cloudy condition of the sky which reduces the amount of incoming solar radiation reaching the earth surface.

يهدف البحث الى التعرف على الجانب النظري للاستثمار فضلا عن بيان دور الاستثمار في تحفيز اقتصاد إقليم كوردستان العراق خلال مدة البحث وتحليل مساهمته في تنشيط كل قطاع من القطاعات الاقتصادية، والعوائق والصعوبات التي تواجه عملية الاستثمار في الإقليم. وكانت مشكلة البحث هل ساهم الاستثمار في الإقليم في تحفيز النشاط الاقتصادي خلال مدة الدراسة. مستنداً على فرضية مفادها أن دور الاستثمار في تحفيز اقتصاد الإقليم كان طرديا ولكن في الوقت نفسه ضئيلاً. وتوصل البحث الى مجموعة من الاستنتاجات من أهمها، ارتفاع حجم الاستثمار في الإقليم بعد صدور قانون الاستثمار رقم (4) لعام 2006، وازدادت بنسبة تقارب784% في العام 2007. ولكن كان هناك قصور في تطبيقه، وتوجهت اغلب الأنشطة الاستثمارية الى الانشطة الخدمية والتوزيعية، بكلام آخر الأنشطة الاقتصادية التي تم الاستثمار فيها معظمها كانت استثمارات عقيمة وغير منتجة ولم تساهم مساهمة حقيقية في النشاط الاقتصادي. فضلاً عن صعوبة تحديد العلاقة وتأرجحها بين نمو الناتج المحلي الاجمالي وحجم الاستثمارات في الاقليم. وكانت أهم المقترحات التي توصل اليها البحث انه من الضروري إعادة النظر في قانون الاستثمار رقم (4)، وتعديله بحيث يوجه عملية الاستثمار الى استغلال هذه الهبات والموارد الاقتصادية وزيادة الناتج الإجمالي الحقيقي من خلال القطاعات الاقتصادية المنتجة.