Even today fires are still utilized by local farmers in Southeast Asia to clear land. Air pollutants produced from the biomass burning activities from Sumatera, for example, are advected towards the western coast of Peninsular Malaysia during the southwest monsoon and can cause adverse effects on the health of the local population. This study utilized the TAPM (The Air Pollution Model) to predict the low level mesoscale characteristics in an equatorial environment that encompassed the island of Sumatera and Peninsular Malaysia during the burning period in August 2005, when persistent haze was prevalent.
TAPM was able to generate the existence of the daily land and sea breeze conditions near the western coast of the Peninsular Malaysia with relative success with a moderately high Index of Agreement of 0.87 and 0.60 for the zonal and meridional wind components, respectively, even without assimilation of local wind conditions. Strong low level southwesterlies that were generated during the daytime over the Straits of Malacca were associated with sea breeze, while weak southeasterlies simulated from 1900 local time towards midnight were associated with land breeze conditions. The vertical wind profile within the lowest kilometer of the atmosphere showed that the weak southwesterlies were present from mid-morning to sunset, which was interspersed with stronger southwesterlies that generally occurred above the height of 400 m.
The meteorological parameters such as wind speed, temperature, and humidity were successfully simulated by the model with comparatively high correlation coefficients, low RMSEs and high indices of agreement with observed values.
The vertical turbulent kinetic energy profiles showed presence of low level suppression at a height below 600 m during the height of the haze in August 2005, which coincided with the intense burning activities in Sumatera and the elevated levels of pollution in western Peninsular Malaysia. Trajectory analysis showed that aged air particles were advected landwards and seawards throughout the duration of the seven days’ simulation from the 7th to the 13th of August 2005. The presence of recirculation features of the land and sea breeze conditions highlighted the poor transportation capability of low level winds that were unable to cope with the high loadings of aerosols from the biomass burning in Sumatera.
Keywords: equatorial region, meteorological parameters, biomass burning, transportation of haze, Southeast Asia.
Wind data measured at three off-shore stations in the northern part of the Adriatic Sea were considered: the Coastal oceanographic station Piran buoy (COSP), the PALOMA tower (the Gulf of Trieste) and the A. ALTA platform (Venice). Annual wind roses for all stations and additional seasonal wind roses for COSP are presented. The Weibull distribution function was applied to wind speed frequency distribution for winds from all directions and separately for bora and sirocco winds. Wind speed frequency distributions for bora winds measured at COSP and PALOMA are bimodal. One peak of this distribution of speeds belongs to nocturnal land breezes and another to bora winds. The peak separation method based on the difference in potential temperature of the atmospheric boundary layer (ABL) between two land stations (Udine and Zagreb) enabled the successful separation of the peaks of bora and land breeze winds. The frequency distribution of the wind speeds changed to the usual unimodal distribution when only those episodes were considered in which the potential temperature of ABL above Udine is higher than that above Zagreb.
Keywords: wind, wind rose, Weibull distribution, northern Adriatic Sea, potential temperature.
In this note we combine two recent findings related to sloped stably-stratified boundary layers (SBL). One of them contrasts Monin-Obukhov height, L, and the low-level jet (LLJ) height, zj, induced by simple katabatic flows. Another result connects turbulent Prandtl number, Pr, to gradient Richardson number, Ri. In this way, one finds the ratio of the two heights (L/zj) as a single value function of the underlying slope and Ri, thus giving a criterion where L may not be the most relevant near-surface layer scaling parameter for turbulent processes. For (L/zj)) > 1 it is the LLJ which determines most of near-surface turbulent properties. This has significant consequences on properties of various near-surface fluxes as treated in NWP, air-chemistry and wind-energy exploring models because most of them deploy L in one or another way for describing the lower boundary condition. This note shows that for ever finer horizontal resolution in our models, L should accommodate slope effects on the near-surface turbulent fluxes.
Keywords: diffusion, parameterization, Prandtl number, gradient Richardson number, stably-stratified turbulence, very stable boundary layers.