Study On Coupling Relationship Between Meteorological Factors And Dynamic Algal Bloom In Taihu Lake

In order to explore the relationship between meteorological factors and dynamic Distribution of Taihu lake algal blooms,81satellite images from2009to2011are selected which algal blooms can be seen obviously. The data source contains two data types, HJ-1A/B, the CCD multi-spectral satellite images and MODIS L1B moderate-resolution satellite images, the spatial resolution of HJ-1A/B satellite images is30*30m, and MODIS L1B moderate-resolution satellite images is250*250m. The main results of this study are summarized as follows:1. For HJ-1A/B multi-spectral satellite images and the MODIS L1B moderate-resolution satellite images, neither near-infrared single-band threshold method nor near-infrared and red band ratio method can extract low concentration algal blooms or remove the information of high suspended water. In contrast, based on the chlorophyll-a concentration value to identify algal blooms in satellite images can avoid these two drawbacks, basically meeting the requirements, extracting algal blooms completely.2. From2009to2011outbreak frequency of algal blooms in Taihu lake decreasing from northwest to southeast. Mild algal blooms broke out more frequently than moderate algal blooms and severe algal blooms. Outbreak frequency of moderate algal blooms decreased year by year while severe algal blooms increased year by year.3. The highest critical temperature for algal blooms breaking out is30℃while there is no minimum critical water temperature. Algal blooms are most vulnerable to break out when water surface temperature is27.2℃,20.9℃and9.8℃in summer, autumn and winter. Algal blooms are most vulnerable to break out when average sunshine time is10.23h,9.31h and7.4h in summer, autumn and winter. Less precipitation in summer and no precipitation in autumn and winter could easily lead to the outbreak of algal blooms. Low wind speed(2m/s or so) making algal particles easy to float up and aggregate, the area of algal blooms will increase rapidly.4. Due to wind and surface air flow, algal blooms are mostly distributing under the direction of the dominant wind direction, wind plays a significantly role in distribution of algal blooms in Taihu lake. From the perspective of short-term weather conditions, When the weather conditions reach the threshold of algal blooms to break out, By simulating high resolution numerical of meteorological elements in the Taihu Lake region, we can predict outbreaks and the evolution of algal blooms, providing meteorological basis for the prediction and warning of algal blooms.