A new approach to forecasting the year-to-year increment of rainfall in North China in July-August (JA) is proposed. DY is defined as the difference of a variable between the current year and the preceding year (year-...A new approach to forecasting the year-to-year increment of rainfall in North China in July-August (JA) is proposed. DY is defined as the difference of a variable between the current year and the preceding year (year-to-year increment). NR denotes the seasonal mean precipitation rate over North China in JA. After analyzing the atmospheric circulation anomalies associated with the DY of NR, five key predictors for the DY of NR have been identified. The prediction model for the DY of NR is established by using multi-linear regression method and the NR is obtained (the current forecasted DY of NR added to the preceding observed NR). The prediction model shows a high correlation coefficient (0.8) between the simulated and the observed DY of NR throughout period 1965-1999, with an average relative root mean square error of 19% for the percentage of precipitation rate anomaly over North China. The prediction model makes a hindcast for 2000-2007, with an average relative root mean square error of 21% for the percentage of precipitation rate anomaly over North China. The model reproduces the downward trend of the percentage of precipitation rate anomaly over North China during 1965-2006. Because the current operational prediction models of the summer precipitation have average forecast scores of 60%-70%, it has been more difficult to forecast the summer rainfall over North China. Thus this new approach for predicting the year-to-year increment of the summer precipitation (and hence the summer precipitation itself) has the potential to significantly improve operational forecasting skill for summer precipitation.展开更多
据预测,内蒙古东部地区未来将出现氮沉降加剧和夏季降水增加的趋势,但大气氮沉降和降水增加都是不可持续的,增加强度可能减弱,也可能出现降低趋势。目前,历史氮、水输入停止后对生态系统的遗留效应尚不明确。本研究基于中国北方温带草...据预测,内蒙古东部地区未来将出现氮沉降加剧和夏季降水增加的趋势,但大气氮沉降和降水增加都是不可持续的,增加强度可能减弱,也可能出现降低趋势。目前,历史氮、水输入停止后对生态系统的遗留效应尚不明确。本研究基于中国北方温带草原长达13年的氮、水添加实验平台,于处理第14年开始定向停止氮、水添加处理,探讨了历史氮、水添加在短期(2年)内对土壤理化性质和微生物学特性的遗留效应。结果表明:停止添加两年后,历史氮添加对铵态氮、硝态氮、可溶性有机碳、氮和速效磷等土壤养分指标的正向遗留效应消失;但对大部分土壤微生物学特性指标仍存在遗留效应,历史15 g N·m^(-2)·a^(-1)添加处理微生物生物量碳、土壤呼吸和碱性磷酸单酯酶活性分别降低73.3%、81.9%和70.3%,表明氮输入停止后微生物学指标的恢复比土壤养分指标慢,具有迟滞效应。相关分析和冗余分析表明,氮对微生物学特性的负向遗留效应与对土壤pH的负向遗留效应有关。历史水添加在处理停止两年后,对土壤pH、铵态氮、可溶性有机碳、氮等以及土壤呼吸、酶活性等仍表现出显著的遗留效应,并与氮沉降的遗留效应存在交互作用。研究结果对预测局域环境改善条件下草地生态系统功能和服务变化趋势及揭示退化草地恢复机制具有重要意义。展开更多
Precipitation prediction is essential for disaster prevention,yet it still remains a challenging issue in weather and climate studies.This paper proposes an effective prediction method for summer precipitation over ea...Precipitation prediction is essential for disaster prevention,yet it still remains a challenging issue in weather and climate studies.This paper proposes an effective prediction method for summer precipitation over eastern China(PEC) by combining empirical orthogonal function(EOF) analysis with the interannual increment approach.Three statistical prediction models are individually developed for respective predictions of the three principal components(PCs) corresponding to the three leading EOF modes for the interannual increment of PEC(hereafter DY;EC).Each model is run for the month of March with two previous predictors derived from sea-ice concentration/soil moisture/sea surface temperature/snow depth/sea level pressure over specific regions.The predicted PCs are projected to the EOF modes derived from observations of DY;EC to produce a new DY;EC.This new DY;EC is then added to the observed PEC of the previous year to obtain the final predicted PEC.The spatial features of the predicted PEC are highly consistent with observations,with the anomaly correlation coefficient skill ranging from 0.32 to 0.64 during 2012-2020.The method is applied for real-time prediction of PEC in 2021.And the results indicate two rain belts located over northeastern China and the Yangtze-Huaihe River valley,respectively,although the chance for the occurrence of a "super" mei-yu with a similar intensity to that in 2020 would be rare in 2021.展开更多
基金Supported by National Basic Research Program of China (Grant No. 2009CB421406)National Natural Science Foundation of China (Grant Nos. 40631005, 40775049)Excellent Ph. D Dissertation in Chinese Academy of Sciences
文摘A new approach to forecasting the year-to-year increment of rainfall in North China in July-August (JA) is proposed. DY is defined as the difference of a variable between the current year and the preceding year (year-to-year increment). NR denotes the seasonal mean precipitation rate over North China in JA. After analyzing the atmospheric circulation anomalies associated with the DY of NR, five key predictors for the DY of NR have been identified. The prediction model for the DY of NR is established by using multi-linear regression method and the NR is obtained (the current forecasted DY of NR added to the preceding observed NR). The prediction model shows a high correlation coefficient (0.8) between the simulated and the observed DY of NR throughout period 1965-1999, with an average relative root mean square error of 19% for the percentage of precipitation rate anomaly over North China. The prediction model makes a hindcast for 2000-2007, with an average relative root mean square error of 21% for the percentage of precipitation rate anomaly over North China. The model reproduces the downward trend of the percentage of precipitation rate anomaly over North China during 1965-2006. Because the current operational prediction models of the summer precipitation have average forecast scores of 60%-70%, it has been more difficult to forecast the summer rainfall over North China. Thus this new approach for predicting the year-to-year increment of the summer precipitation (and hence the summer precipitation itself) has the potential to significantly improve operational forecasting skill for summer precipitation.
文摘据预测,内蒙古东部地区未来将出现氮沉降加剧和夏季降水增加的趋势,但大气氮沉降和降水增加都是不可持续的,增加强度可能减弱,也可能出现降低趋势。目前,历史氮、水输入停止后对生态系统的遗留效应尚不明确。本研究基于中国北方温带草原长达13年的氮、水添加实验平台,于处理第14年开始定向停止氮、水添加处理,探讨了历史氮、水添加在短期(2年)内对土壤理化性质和微生物学特性的遗留效应。结果表明:停止添加两年后,历史氮添加对铵态氮、硝态氮、可溶性有机碳、氮和速效磷等土壤养分指标的正向遗留效应消失;但对大部分土壤微生物学特性指标仍存在遗留效应,历史15 g N·m^(-2)·a^(-1)添加处理微生物生物量碳、土壤呼吸和碱性磷酸单酯酶活性分别降低73.3%、81.9%和70.3%,表明氮输入停止后微生物学指标的恢复比土壤养分指标慢,具有迟滞效应。相关分析和冗余分析表明,氮对微生物学特性的负向遗留效应与对土壤pH的负向遗留效应有关。历史水添加在处理停止两年后,对土壤pH、铵态氮、可溶性有机碳、氮等以及土壤呼吸、酶活性等仍表现出显著的遗留效应,并与氮沉降的遗留效应存在交互作用。研究结果对预测局域环境改善条件下草地生态系统功能和服务变化趋势及揭示退化草地恢复机制具有重要意义。
基金sponsored by the National Natural Science Foundation of China [grant numbers 420881014199128342025502]。
文摘Precipitation prediction is essential for disaster prevention,yet it still remains a challenging issue in weather and climate studies.This paper proposes an effective prediction method for summer precipitation over eastern China(PEC) by combining empirical orthogonal function(EOF) analysis with the interannual increment approach.Three statistical prediction models are individually developed for respective predictions of the three principal components(PCs) corresponding to the three leading EOF modes for the interannual increment of PEC(hereafter DY;EC).Each model is run for the month of March with two previous predictors derived from sea-ice concentration/soil moisture/sea surface temperature/snow depth/sea level pressure over specific regions.The predicted PCs are projected to the EOF modes derived from observations of DY;EC to produce a new DY;EC.This new DY;EC is then added to the observed PEC of the previous year to obtain the final predicted PEC.The spatial features of the predicted PEC are highly consistent with observations,with the anomaly correlation coefficient skill ranging from 0.32 to 0.64 during 2012-2020.The method is applied for real-time prediction of PEC in 2021.And the results indicate two rain belts located over northeastern China and the Yangtze-Huaihe River valley,respectively,although the chance for the occurrence of a "super" mei-yu with a similar intensity to that in 2020 would be rare in 2021.
