Suchergebnisse

Change in structure of land surface can affect atmospheric boundary layer and formation of internal boundary layer. This will change shear stresses and turbulent boundary layer. Change in low level wind shear and turbulent can affect air craft performance and has potentially adverse effects on flight safety during landing and taking-off stages. In this study, change in land area around Baghdad Airport and its effects on structure of boundary layer and radix layer through summer season (July from years 1985 and 2014) is examined. The examination is done through atmospheric data of radiosonde (at altitude more than 1500 m) and remote sensing by Landsat 5 and 8 images (circular region around airport has radius 3.250 km and the airport is considered the center of this circle). From analysis of hourly wind speed and temperature profile with height observed by radiosonde, change in convective radix layer can be determined at this period resulted from change structure of boundary layer depending on characteristic of landcover used in supervised classification. Building area increases from 18% in 1985 to 41% in 2014. These results enforced by positive values of built up index BI, that showed a decreases in 2014. All these elements changed convective radix layer from less than 500 m in summer 1985 to more than 700 m. There is a large fluctuation in radix layer height depended on convective and friction velocity at 2014 data. Thus indirect change in structure of convective layer will affect navigation movement of Baghdad International Airport.

Heat island is known as the increases in air temperature through large and industrial cities compared to surrounding rural areas. In this study, remote sensing technology is used to monitor and track thermal variations within the city center of Baghdad through Landsat satellite images and for the period from 2000 to 2015. Several processors and treatments were applied on these images using GIS 10.6 and ERDAS 2014, such as image correction and extraction, supervised classification, and selection of training samples. Urban areas detection was resulted from the supervised classification linked to the temperature readings of the surface taken from the thermal bands of satellite images. The results showed that the surface temperature of the city of Baghdad increased by 8 degrees Celsius in 15 years. This is due to the increase in the expansion of the urban areas type of land use, where the human activity, especially after 2003, caused increased buildup area to about 198.41 km2. All these changes occurred at the expense of many green regions which were reduced, with the transformation of open and agricultural areas to residential, commercial, and industrial uses. Increases in surface temperature resulted increases in air temperature, where the minimum temperature showed larger increases relative to maximum temperature (about 1.44 and 0.76 ºC, respectively).

The lowest layer of the atmosphere is called the atmospheric mixed layer, characterized by small-scale, irregular air motions defined by winds that change in speed and direction. Aerosol radiative effects impact the atmospheric boundary layer (ABL), which holds most aerosols in the lower atmosphere. Aerosol absorption and scattering both lower the quantity of solar energy that reaches the ground, which has an impact on the spectral signature of the land coverings. In this study, 51 locations in downtown Baghdad were chosen for four different types of land cover (water bodies, farms, open areas, and residential areas) for Sentinel 2 satellite imagery, and the time the pictures were taken was 8:00 am ( 22 March, 22 June, 20 September, and 22 December) 2021. Their spectral reflectance was calculated at the NIR band using a mathematical equation in the ArcGIS program for Sentinel 2 satellite images that had been processed and analyzed. Also, atmospheric boundary layer height and solar radiation values were downloaded for the same date as the satellite images and compared with the spectral reflectivity values of the land covers(agriculture area, residential area, open area, and river) and knowing the effect of the mixing layer and solar radiation on the spectral reflectance values. The highest value of spectral reflectivity, mixing layer height, and solar radiation was in June at (0.065, 1965.524629, and 897.7088) respectively. The spectral reflectivity of plants at near-infrared (NIR) was higher than the rest of the earth's features because plants reflect near-infrared radiation and absorb the red and blue parts of the spectrum.

Stability in the atmosphere is the most important factor in the transport and dispersion of air pollutants. There are a number of complicated methods for determining stability. The majority of these methods are based on the amount of convective and mechanical turbulence in atmospheric motions, such as the Richardson number, Monin-Obukhov length, Pasquill-Gifford stability classification, and Pasquill-Turner stability classification. Pasquill utilized surface-accessible meteorological information like breeze speed, sun-based radiation, and surface darkness to portray air steadiness. Baghdad territory was separated into a gathering of focuses as indicated by scope and longitude; six focuses were chosen and conveyed in a manner that addresses all districts of Baghdad territory through the diurnal hourly information (6, 9, 12, 15, 18) for the months (January, April, July, October) for the year 2018, and find the spatial and fleeting circulation of relative recurrence RF% dependability classes as per consolidating the Pasquill-Turner strategy. The pattern of conditions necessary for atmospheric stability can be derived from two distinct categories. First, the patterns for the month and the season are calculated. The results show that in April, the relative frequency (RF%) of the (A) and (B) classes is highest in the northeast of Baghdad province and has an inverse relationship with average wind speed (R = - 0.62, - 0.90). During July, the relative frequency RF percentages of the (C) and (D) classes are highest in the west and northeast of Baghdad province, respectively, and they are positively correlated with average wind speed (R = 0.91, 0.78, respectively). The spatial and worldly conveyance of relative recurrence RF% steadiness classes as per joining the Pasquill-Turner strategy prompts a feeble relationship or an absence of clarity in the relationship because of the impact of affecting elements (non-direct variety) (the Pasquill-Turner Technique (PTM) in extra factors of the Pasquill strategy). Second, monthly and seasonal patterns are calculated. The Pasquill method reveals that the stability class (C) has the highest relative frequency (RF%) in January (28.72 percent), the stability class (B) has the highest relative frequency (RF%) in April (33.98 percent), the stability class (C) has the highest relative frequency (RF%) in July (64.74 percent), and the stability class (C) has the highest relative frequency (RF%) in October (35.48 percent).