Kenobi Isima Morris

One of the worst haze events to ever hit Peninsular Malaysia occurred in June 2013 due to smoke from Riau, Central Sumatra. While biomass-burning in the region is common, the early occurrence of a haze episode of this magnitude was uncharacteristic of the seasonality of extreme fire events, which usually occur between August and October in the Maritime Continent (MC). This study aims to investigate the phenomenology of the June 2013 haze event and its underlying meteorological forcing agents. The aerosol and meteorological environment during the event is examined using the Moderate Resolution Imaging Spectroradiometer (MODIS) active fire hotspot detections and aerosol optical thickness retrievals, satellite-based precipitation retrievals, and meteorological indices. These datasets are then supported by a WRF-Chem simulation to provide a comprehensive picture of the event’s meteorology and aerosol transport phenomenology. While extreme fire events are more characteristic of El Nino years, the MODIS fire count over the MC in June for the years 2001–2015 was highest in 2013 when neutral El Nino/Southern Oscillation (ENSO) conditions prevailed. Although, the mean daily precipitation for June 2013 was below average for June 2003–2015. An early active tropical cyclone (TC) season occurred in 2013, and results show that the combined induced subsidence and flow enhancement due to TC Bebinca and the dry phases of a strong Madden–Julian Oscillation (MJO) event contributed to the event intensification. Results also show that Bebinca induced a decrease in surface relative humidity of at least 10% over Riau, where fire hotspots were concentrated.

The urban boundary layer (UBL) is the internal advection layer of atmosphere above urban region which determines the exchanges of momentum, water and other atmospheric constituents between the urban land surface and the free troposphere. This paper tested the performance of three planetary boundary layer (PBL) physics schemes of Weather Research and Forecast (WRF) software to ensure the appropriate representation of vertical structure of UBL in Greater Kuala Lumpur (GKL). Comparison was conducted on the performance of respective PBL schemes to generate vertical and near-surface weather profile and rainfall. Mellor-Yamada- Janjíc (MYJ) local PBL scheme coupled with Eta MM5 surface layer scheme was found to predict the near-surface temperature and wind profile and mixing height better than the nonlocal schemes during the intermonsoonal period with least influences of the synoptic background weather.

The Antarctic continent is known to be an unpopulated region due to its extreme weather and climate conditions. However, the air quality over this continent can be affected by long-lived anthropogenic pollutants from the mainland. The Argentinian region of Ushuaia is often the main source area of accumulated hazardous gases over the Antarctic Peninsula. The main objective of this study is to report the first in situ observations yet known of surface ozone (O₃) over Ushuaia, the Drake Passage, and Coastal Antarctic Peninsula (CAP) on board the RV Australis during the Malaysian Antarctic Scientific Expedition Cruise 2016 (MASEC’16). Hourly O₃ data was measured continuously for 23 days using an EcoTech O₃ analyzer. To understand more about the distribution of surface O₃ over the Antarctic, we present the spatial and temporal of surface O₃ of long-term data (2009–2015) obtained online from the World Meteorology Organization of World Data Centre for greenhouse gases (WMO WDCGG). Furthermore, surface O₃ satellite data from the free online NOAA-Atmospheric Infrared Sounder (AIRS) database and online data assimilation from the European Centre for Medium-Range Weather Forecasts (ECMWF)-Monitoring Atmospheric Composition and Climate (MACC) were used. The data from both online products are compared to document the data sets and to give an indication of its quality towards in situ data. Finally, we used past carbon monoxide (CO) data as a proxy of surface O₃ formation over Ushuaia and the Antarctic region. Our key findings were that the surface O₃ mixing ratio during MASEC’16 increased from a minimum of 5 ppb to ~ 10–13 ppb approaching the Drake Passage and the Coastal Antarctic Peninsula (CAP) region. The anthropogenic and biogenic O₃ precursors from Ushuaia and the marine region influenced the mixing ratio of surface O₃ over the Drake Passage and CAP region. The past data from WDCGG showed that the annual O₃ cycle has a maximum during the winter of 30 to 35 ppb between June and August and a minimum during the summer (January to February) of 10 to 20 ppb. The surface O₃ mixing ratio during the summer was controlled by photochemical processes in the presence of sunlight, leading to the depletion process. During the winter, the photochemical production of surface O₃ was more dominant. The NOAA-AIRS and ECMWF-MACC analysis agreed well with the MASEC’16 data but twice were higher during the expedition period. Finally, the CO past data showed the surface O₃ mixing ratio was influenced by the CO mixing ratio over both the Ushuaia and Antarctic regions. Peak surface O₃ and CO hourly mixing ratios reached up to ~ 38 ppb (O₃) and ~ 500 ppb (CO) over Ushuaia. High CO over Ushuaia led to the depletion process of surface O₃ over the region. Monthly CO mixing ratio over Antarctic (South Pole) were low, leading to the production of surface O₃ over the Antarctic region.

Rapid urbanization of cities has greatly modified the thermal and dynamic profile in the urban boundary layer. This paper attempts to study the interaction of urban heating and the local topographic‐induced flow circulation for a tropical coastal city, Greater Kuala Lumpur, in Malaysia. The role of sea‐and‐valley‐breeze‐orientated synoptic flow (SBOS) on the interaction is determined by comparing two intermonsoon periods. A state‐of‐the‐art numerical model, Advanced Research Weather Research and Forecasting model, is used to identify the influence of urbanization through modification of urban surfaces. The model reasonably reproduces the vertical sounding data and near‐surface weather parameters. The diurnal urban heating pattern is attributed to three predominant factors: (i) weak under calm and clear‐sky condition (morning heating), (ii) weak under larger atmospheric moisture content (late afternoon convection), and (iii) largest (1.4°C) due to differential cooling rate of urban and rural surface at night. The interaction of urban thermals and upper level SBOS affects the effect of urbanization on local circulation during the day. The urban thermals reduce the weak opposing SBOS (2 m s⁻¹) suppresses the vertical lifting of urban thermals and decelerates the sea breeze front. It is discovered that the interaction of urban heating and topographic‐induced flow is interdependent while the synoptic flow plays a critical role in modifying both factors, respectively.