Fuyi Tan

AERONET data-based determination of aerosol types

Aerosols are among the most interesting topics investigated by researchers because of their complicated characteristics and poor quantification. Moreover, significant uncertainties are associated with changes in the Earths radiation budget. Previous studies have shown numerous difficulties and challenges in quantifying aerosol influences. In addition, the heterogeneity from aerosol loading and properties, including spatial, temporal, size, and composition features, presents a challenge. In this study, we investigated aerosol characteristics over two regions with different environmental conditions and aerosol sources. The study sites are Penang and Kuching in Malaysia, where a ground-based AErosol RObotic NETwork (AERONET) sun-photometer was deployed. The types of aerosol, such as biomass burning, urban/industrial, marine, and dust aerosols, for both study sites were identified by analyzing aerosol optical depth and angstrom exponent. Seasonal monsoon variation results in different aerosol optical properties, characteristics, and types of aerosols that are dominant in Penang and Kuching. Seasonal monsoon flow trend patterns from a seven-day back-trajectory frequency plotted by the Hybrid Single-Particle Lagrangian Integrated Trajectory model illustrated the distinct origins of trans-boundary aerosol sources. Finally, we improved our findings in Malaysian sites using the AERONET data from Singapore and Indonesia. Similarities in the optical properties of aerosols and the distribution types (referred to as homogeneous aerosol) were observed in the Penang-Singapore and the Kuching-Pontianak sites. The dominant aerosol distribution types were completely different for locations in the western (Penang-Singapore) and eastern (Kuching-Pontianak) parts of the South China Sea. This is a result of spatial and temporal heterogeneity. The spatial and temporal heterogeneities for the western and eastern portions of South China Sea provide information on the natural or anthropogenic processes that take place.

The effects of orography in indochina on wind, cloud, and rainfall patterns during Typhoon Ketsana (2009)

The objective of this study is to i) investigate the effects of orography on the rainfall, wind, and cloud systems of the Typhoon Ketsana (2009) in Indochina, ii) determine rainfall distribution patterns and which parts of Indochina were most affected during Typhoon Ketsana, iii) identify trends in the cloud and rainfall distribution patterns and wind flow patterns in the synoptic scale on orographic effects during Typhoon Ketsana. Remote sensing techniques have been used to study the impacts of TCs. Using data from the remote sensing data such as Fengyun 2D (FY-2D) satellite, Global Digital Elevation Model (GDEM) from the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) satellite, wind information from the Navy Operational Global Atmospheric Prediction System (NOGAPS), and radiosonde data were applied in this study to determine the relationship of the typhoon with the orographic effect. This study provides examples of how the orographic effect is important to weather forecasters, as high mountain ranges were able to influence the distribution of the cloud, rainfall and even wind flow patterns during the typhoon season. This remote sensing technique allows tropical cyclones to be forecasted and their impacts to be defined, and it allows disaster zones to be determined.

Comparison of Aerosol optical depth (AOD) derived from AERONET sunphotometer and Lidar system

Aerosol optical depth (AOD) is the measure of aerosols distributed within a column of air from the instrument or Earths surface to the top of the atmosphere. In this paper, we compared the AOD measured by the Raymetrics Lidar system and AERONET sunphotometer. A total of 6 days data which was collected by both instruments were compiled and compared. Generally, AOD value calculated from Lidar data are higher than that calculated from AERONET data. Differences and similarities in the AOD data trend were observed and the corresponding explanations were done. Level 1.5 data of AERONET is estimated to have an accuracy of ±0.03, thus the Lidar data should follow the trend of the AERONET. But in this regards, this study was conducted less than one month and was very difficult to justify the differences and similarities between AOD measured by the Raymetrics Lidar system and AERONET sunphotometer. So further studies for an extended period will be needed and performed with more comprehensive LIDAR measurements. The slope of the best-fit straight line for the data points between the AOD values retrieved from LIDAR and the AERONET measurements is the closest to unity and the coefficient of determination is high (above 0. 6692). Factors which affect AOD data were discussed. As a conclusion, the trends of the AOD of both systems are similar. Yet due to some external factors, the trend will be slightly different.

PM10, PM2.5 and PM1 distribution in Penang Island, Malaysia

Particulate Matter (PM) consist of tiny solid or liquid particles that floating freely in the air. PM10 refers to the particles which have size up to 10 microns (μm). The smaller the particle size (such as PM1), the more severe it will affect our human health if we inhaled too much into our lungs. In this paper, we used the DustTrack{trade mark, serif} Aerosol Monitor with Model 8520 to obtain the PM distribution (PM10, PM2.5 and PM1) in Penang Island. The in-situ measurement was taken on 10 August 2012 at Georgetown, Batu Ferringhi and Permatang Damar Laut open area. The data obtained was analyzed and interpreted. The results show that the dust level at Permatang Damar Laut was low as compare to the other two areas which are located in town area. The highest PM10, PM2.5 and PM1 dust level with an averaging time of 6 hours was observed at Batu Ferringhi with a reading of 200, 194 and 185μg/m3. This study can provide a guideline to detect and monitor the dust level at Penang Island. Further study can be done to monitor the temporal changes of air quality over Penang Island, Malaysia.

Preliminary analysis of ground based lidar backscattered signal and performance evaluation in Penang Island

Lidar is a widely used instrument by scientists around the world because of its high temporal and spatial resolution. With these characteristics, the interpretation of lower atmosphere behavior is improved, especially for the structure of the boundary layer, strongly related to air quality in the region. For the first time a backscattering lidar with wavelength 355 nm and Raman capabilities produced by Raymetrics was operated in Universiti Sains Malaysia (USM) in Penang Island. Due to operational constraints, this study will only discuss backscattering signal at 60 degrees zenithal angle shooting. From this study, we found that the lidar signal was extinguished very quickly and with maximum range of 3 kilometers for 30 seconds temporal resolution. The signal was extremely noisy in this study and even after subtracting the backgrounds such as solar radiation in the range corrected signal. Dead-time correction was then applied to improve the lidar signal. The better signal for the near and far ranges of this angle shooting, gluing both analog and photon is necessary. Temporal evolution was plotted to determine the planetary boundary layer (PBL) structure and the altitude of PBL also can be identified. Moreover, cloud distribution and aerosol concentration pattern can be structured from the temporal evolution graph. However, for identifying the tendency of PBL structure in Penang Island, longer period and continuous data acquisition were needed.

Analysis of Ozone column burden in Peninsular Malaysia retrieved from Atmosphere Infrared Sounder (AIRS) data: 2003–2009

Ozone (O3) is a radiatively active trace gas that plies important role in atmosphere heating rates because of its good ability to absorb the infrared radiation and occur both at the ground level and naturally in the earths upper atmosphere. Results from the analysis of the retrieved monthly (AIRX3STM) 1°×1° spatial resolution Atmosphere infrared sounder (AIRS) data were utilized to analyze the distribution of O3 column burden in Peninsular Malaysia for the period 2003–2009. AIRS is one of the several instruments onboard the Earth Observing System (EOS), onboard NASAs Aqua Satellite, launched on May 4, 2002. The analysis of O3 above five dispersed stations in study area shows the seasonal variation in the O3 values fluctuated considerably between wet and dry periods, and O3 values strongly correlated with weather conditions. The lowest O3 observed during rainy months, low temperature and low sunshine hours, vice versa. The highest O3 values occurred over Industrial and congested urban zones. The monthly O3 maps were generated, to study O3 distribution over peninsular Malaysia for 2009, using Kriging Interpolation technique. The AIRS data and the Satellite measurements are able to measure the increase of the atmosphere O3 concentrations over different regions.

Investigation of aerosol distribution patterns and its optical properties at different time scale by using LIDAR system and AERONET

Atmospheric aerosol is a major health-impairment issue in Malaysia especially during southeast monsoon period (June-September) due to the active open burning activities. However, hazy days were an issue in Penang, Malaysia during March, 2014. Haze intruded Penang during March and lasted for a month except for the few days after rain. Rain water had washed out the aerosols from the atmosphere. Therefore, this study intends to analyse the aerosol profile and the optical properties of aerosol during this haze event and after rain. Meanwhile, several days after the haze event (during April, 2014) were also analyzed for comparison purposes. Additionally, the dominant aerosol type (i.e., dust, biomass burning, industrial and urban, marine, and mixed aerosol) during the study period was identified according to the scattering plots of the aerosol optical depth (AOD) against the Angstrom exponent.

Multiple regression method to determine aerosol optical depth in atmospheric column in Penang, Malaysia

Aerosol optical depth (AOD) from AERONET data has a very fine resolution but air pollution index (API), visibility and relative humidity from the ground truth measurements are coarse. To obtain the local AOD in the atmosphere, the relationship between these three parameters was determined using multiple regression analysis. The data of southwest monsoon period (August to September, 2012) taken in Penang, Malaysia, was used to establish a quantitative relationship in which the AOD is modeled as a function of API, relative humidity, and visibility. The highest correlated model was used to predict AOD values during southwest monsoon period. When aerosol is not uniformly distributed in the atmosphere then the predicted AOD can be highly deviated from the measured values. Therefore these deviated data can be removed by comparing between the predicted AOD values and the actual AERONET data which help to investigate whether the non uniform source of the aerosol is from the ground surface or from higher altitude level. This model can accurately predict AOD if only the aerosol is uniformly distributed in the atmosphere. However, further study is needed to determine this model is suitable to use for AOD predicting not only in Penang, but also other state in Malaysia or even global.

Investigation of in-situ measurement of pollutant gases over Penang island

Penang Island is experiencing rapid development in house construction and industrial activity which caused air pollution problems getting worst. Furthermore, with recent forest burning in Indonesia, the situation was become serious. Due to the increasing in air pollution problems, we decided to carry out an investigation of air pollution over Penang Island. In this paper, we used Aeroqual Series 500 Monitor (for NO2 and O3) and MultiRAE-IR Model PGM-54 (for CO2) to perform in-situ ground level measurement over Penang Island. All measurement has been carried out every 5km journey around the Penang Island. From the data obtained, the changes of NO2, O3 and CO2 pollutant gasses concentration over time can be study and further investigate.

Relationship between orography and the wind-cloud systems of tropical cyclones

Abstract. We investigate the effect of orography on the relationship of wind-cloud systems with tropical cyclones (TC). The impact of orography is important for the cloud distribution and wind flow patterns of TC activity. Furthermore, the influence of orography on TCs remains unclear and is an active area of scientific research because of the complexity of orography effects caused by the presence of mountains. We focus on typhoons in the open sea, near coastal regions, and in the mountains. The atmospheric circulation of the level between the troposphere and the stratosphere (TS level) varies when disturbances, such as a high mountain range, occur in the surrounding edges or outflow of a typhoon. Orographic effects can influence the types of clouds (e.g., nimbus and cirrus) that form in different altitudes (high, middle, and low levels of the troposphere). Our results imply that the interaction between TCs and high-altitude topography (e.g., mountains) leads to changes in the features of TCs.