新一代地球观测信息在天然气水合物研究中的应用展望

地球上蕴藏着巨大的天然气水合物(GasHydrates)矿藏,它可作为一种新的烃类资源来开发利用。天然气水合物中CH4的释放影响全球气候变化。同时,天然气水合物是一种潜在的环境灾害诱发因素。天然气水合物的研究与开发目前在国内外成为研究热点。新一代地球观测信息,如已发射成功的TERRA中的MODIS、MOPITT信息以及即将发射的化学星CHEM为天然气水合物的研究与开发提供了新的技术方法。中国气候观测系统中观测台站观测信息的共享,加速了开发利用新一代地球观测信息的速度,也必将促进新一代地球观测信息在天然气水合物研究中发挥更大的作用。     

Analysis of satellite imagery using a simple algorithm supports evidence that Trichodesmium supplies a significant new nitrogen load to the GBR lagoon

This work supports previous studies in the Great Barrier Reef lagoon that show the new nitrogen (N) load introduced by Trichodesmium is similar to or greater than that from riverine discharges. However, the current management programs aimed at improving the chronic eutrophic state of the GBR ignore the N load from Trichodesmium. These programs also ignore the evidence that Trichodesmium blooms could promote the bioavailability of heavy metals and be a source of toxins in the ciguatera food chain. Further work is urgently required to better quantify the potential impacts of Trichodesmium and develop management plans to reduce those impacts. A simple algorithm that uses MODIS imagery is developed for not only monitoring the spatial extent of Trichodesmium blooms but also for quantifying the concentration of those blooms. The algorithm is based on the readily available MODIS L2 data. A management plan that includes the harvesting of Trichodesmium is outlined.     

A focus group study of factors that promote and constrain the use of satellite-derived fire products by resource managers in southern Africa

Semi-structured focus group interviews were employed to examine factors that affect the likelihood that resource managers in southern Africa will use information on vegetation fires provided by two satellite-derived products: an active fire product and a burned area product. The two products are updated regularly and aim to deliver the state-of-the-art in the global monitoring of fires from satellite remote-sensing. Both products are derived from data transmitted by the Moderate Resolution Imaging Spectroradiometer (MODIS) sensors carried onboard NASA's Aqua and Terra satellites. The active fire product can be accessed for free via the internet and on media by users working anywhere in the world; the burned area product will be accessible in a similar manner in 2006. The MODIS fire products provide systematic, near-global coverage and are freely available; as such, they give resource managers new opportunities to obtain or supplement information they need to manage vegetation fires effectively. However, the availability of these products does not mean that resource managers will use them, and many other factors are involved. To understand factors that affect whether southern African resource managers will use the two products, two focus groups were held with members of the Southern African Fire Network (SAFNet) in Malawi, Africa, August 2004. Analysis of the group discussions reveals a number of factors that influence whether they will use the products. The qualitative, in depth nature of the group discussions revealed 12 main factors that influence product use; not least the low international internet bandwidths for African countries outside of South Africa. Analysis of the group discussions also suggests how the uptake of MODIS fire products by resource managers in southern Africa might be enhanced by affecting specific changes to how MODIS products are packaged and delivered.     

Sensitivity of modelled gross primary productivity to topographic effects on surface radiation: A case study in the Cotter River Catchment, Australia

Gross primary productivity (GPP) is a critical response variable for many environmental problems, including terrestrial carbon accounting and the calculation of catchment water balances. Various approaches for modelling GPP have been developed and applied at continental and landscapes scales, but little attention has been given to the sensitivity of GPP to the spatial scale of its driving variables. A key driving variable is surface radiation (R_s) which is influenced by both meso-scale factors (latitude, time of year, cloudiness) and the topographic variables of slope, aspect and horizon shading. We compared the sensitivity of modelled GPP to two different sources of surface radiation (R_s): (1) the ANUCLIM method which only captures the meso-scaled factors; and (2) the SRAD method which incorporates the topographic effects GPP was calculated using the radiation use efficiency (RUE) model (Roderick et al., 2001) to discern general patterns of vegetation productivity at a sub-catchment (i.e. sub-water shed) scale. The radiation use efficiency approach uses the normalized difference vegetation index (NDVI) derived from satellite data (MODIS TERRA), along with estimates of solar radiation at the top of the atmosphere (R_o) and canopy (R_s). In this approach, R_o and R_s capture the influence of diffuse irradiance in canopy photosynthesis and vegetation productivity respectively. This research showed that R_s calculated using the SRAD program provides important discrimination of GPP regimes at a sub-catchment scale, as the result of minimum and maximum daily radiation varying between shaded and exposed surfaces. However, mean daily radiation at a whole-of-catchment scale did not differ between the two sources as the differences in the minimum and maximum daily values tend to cancel each other out. Applications of GPP models therefore need to consider whether topographic factors are important and select the appropriate source of R_s values. GPP models should also reflect understanding of radiation use efficiency. However, further research is required especially with respect to the influence of water stress on plant response.     

基于MODIS数据的云南省地表温度反演研究

基于MODIS数据反演云南省地表温度,采用分裂窗算法需要参数较少、易实现。研究表明:云南省地表温度由北向南递增,东部高、西部低,基本符合云南省实际情况。利用气象观测站实测数据进行验证,平均误差为3.16℃,两组数据基本接近,证明基于MODIS数据和分裂窗算法反演云南省地表温度是可行的。     

Estimation of Southeast Asian rice paddy areas with different ecosystems from moderate-resolution satellite imagery

Multi-temporal satellite imagery from the Moderate Resolution Imaging Spectrometer (MODIS) was used to map the different ecosystems of Southeast Asian (SEA) rice paddies. The algorithm was based on temporal profiles of vegetation strength and/or water content, using MODIS surface reflectance in visible to near-IR range. The results obtained from the analysis were compared to national statistics. Estimated SEA regional rice area was 42 × 10⁶ ha, which agrees with published values. The model performance was dependent on rice ecosystems. Good linear relationships between the model results and the national statistics were observed for rainfed rice. High linear coefficients of determination, R², were also found for irrigated rice and upland rice, but the model tended to underestimate irrigated rice and overestimate upland rice. However, these high R² values indicated that the model effectively simulated spatial distribution of these rice areas. These R² values were either of similar magnitude or larger than those reported in literature, regardless of the rice ecosystem. Poor correlation was observed for deepwater rice.     

基于MODIS AOD数据的南京市大气能见度估算

以南京市为研究区,利用MODIS气溶胶产品数据(MOD04L2)获取研究区气溶胶标高数据,结合地面气象站点能见度观测数据,构建研究区不同季节能见度估算模型,估算南京市2013年能见度时空分布。研究结果表明,研究区能见度模型估算值与实测值总体趋势较为一致,分季节模型能见度估算均值相对误差为14.3%;南京市2013年能见度年均值为6.07km,大致呈现出由市区向周边郊区逐渐升高的趋势;研究区不同季节能见度差异明显,夏季能见度显著高于其他3个季节,在该季节全市能见度均值达到9.93km,约为其余3个季节均值的2倍左右,气候状况与经济社会发展布局是影响研究区能见度时空差异的主要因素。     

安徽及周边地区气溶胶时空特征及成因分析

利用AERONET数据对2013年6月—2014年5月Aqua/MOIDS气溶胶产品在安徽及周边地区的适用性进行了验证,分析了气溶胶时空分布特征并讨论其影响因素.结果表明:MODIS AOD与AERONET数据在研究区具有很好的一致性,满足美国国家宇航局(NASA)的误差要求.时间上,安徽北部及中部春季、冬季AOD值较高,合肥-南京一带在冬季AOD值甚至高于0.9;研究区域整体在秋季达到AOD最低值.空间上,皖西、皖南山区和庐山等高海拔地区AOD较低,而处于山区间的沿江平原的AOD却明显升高,形成一个以沿江平原为高值中心的环形分布区.研究区域内AOD与能见度、相对湿度的相关性显著,风速对AOD有着先促进后抑制的影响,经济发展和人口分布对气溶胶的分布也有着明显的影响.     

黄河源植被时空变化及其对地形和气候的响应

基于2000~2019年MODIS归一化植被指数（NDVI）遥感数据,辅以同期气温、降水和地形数据,通过最大值合成、趋势分析及相关分析法,分析了黄河源区植被的时空变化特征及其对地形和气候变化的响应.结果表明：黄河源区植被NDVI整体处于中高水平,但空间差异显著,呈现由东南向西北递减的空间分布格局;近20a来,植被总体上呈现出变好的趋势.植被对高程和坡度响应明显,随着高程的增加,植被NDVI呈现先增加后减少的趋势,但在3500~4100m区间植被NDVI变化不显著;此外,植被NDVI随着坡度的增大呈现出先增大后减小的变化趋势,且在24~26°坡度带植被NDVI达到最大值.黄河源区植被受气温和降水的共同影响,与降水相比,气温对黄河源区植被变化的影响更为显著.     

MODIS遥感气溶胶光学厚度产品在地面能见距中的应用

利用气象站点能见距的历史资料和NASA的MOD1S卫星遥感手段获取10km＊10km分辨率的气溶胶光学厚度资料，建立二者之间的季节平均关系。得到了上海地区季节变化的气溶胶标高，并利用标高数据和气溶胶光学厚度的季节分布。反演出上海地区季节变化的区域能见距分布，研究近地层大气气溶胶与地面能见距的关系，分析上海市能见度时空分布特征，结果显示：上海城区在冬春季平均能见距较差，市区中心能见距在lOkm以下；低能见距中心分布明显。且主要分布在杨浦、桃浦、吴淞等工业区范围。