ATMOSPHERIC RESIDUAL LAYER HEIGHT VARIATIONS IN CLEAR AND RAINY DAY BASED ON HIGH RESOLUTION RADIOSONDE AND GLOBAL POSITIONING SYSTEM RADIO OCCULTATION DATA

• Main Author: Pratikasari, Resa
• Format: Theses
• Language: Indonesia
• Online Access: https://digilib.itb.ac.id/gdl/view/50952
• Institution: Institut Teknologi Bandung

Local climate conditions, rainfall patterns, location, and atmospheric circulation are some of the factors that influence the structure and variation of the Planetary Boundary Layer (PBL) which greatly affects the variation of the residual layer. Residual layer is an atmospheric layer that occurs at night time, this layer is a former of mixed layers that occurs during daytime. In this study, I used high resolution radiosonde and Global Positioning Radio Occultation System (GPS-RO) data to estimate residual layer and mixed layer height that represents Planetrary Boundary Layer (PBL) height. I also analyzed the variation of residual layers height in clear and rainy day and analyzed its effects on the variation of mixed layers height. Residual layer and mixed layer height are estimated based on reactivity (N) variable using the vertical gradient method. The results based on radiosonde and GPS-RO data show that in clear day the residual layer height at the beginning of the night will be the same as the mixed layer height in the afternoon. The residual layer height continues to fall until sunrise. Meanwhile, in rainy days if the rain occurs until evening (cross the sunset), then after the rain residual layer will not form, this is because no capping inversion formed in the afternoon. And if the rain stops before sunset capping inversion will be formed even at very low height so that the residual layer at night will also be low. Based on the analysis of the residual layer height variation, it is known that the residual layer height at the night did not affect the variation of mixed layer height in the morning although the residual layer provides a favorable thermal condition for the growth and development of the mixed layer. The variation of mixed layer in the morning is more affected by weather conditions at that time. While the variation of residual layer height at the beginning of the night (19.00 - 22.00 LT) is strongly affected by the dynamics of the weather in the afternoon (15.00 - 17.00 LT). Climatologically, the average of the residual layer height is lower in the rainy season than in the dry season. And spatially, the average of the residual layer height is lower in areas near the equator line than other regions in Indonesia. In general, analysis of residual layer height at 19.00 - 22.00 LT can be used to analyze the variation and the dynamics of PBL in an area, because the physical composition and variation of residual layer height at 19.00 - 22.00 LT are the same as the mixed layer (representing PBL) at 15.00 - 17.00 LT which is the time of PBL reached its maximum value of height.