Knowledge Resource Center for Ecological Environment in Arid Area
| 干旱对印度农业的影响及CMIP5对印度极端气候的预估 | |
| 其他题名 | Impact of drought on agriculture and CMIP5 model projections of extreme climate events in India |
| RESHMITA NATH | |
| 出版年 | 2017 |
| 学位类型 | 博士 |
| 导师 | 陈文 |
| 学位授予单位 | 中国科学院大学 |
| 中文摘要 | 近几十年来, 印度夏季发生了一系列极端干旱和洪涝事件。对于印度来说，降水的季节性极强，而农业用水绝大部分依赖自然降水。最强降水分布在夏季6-9月的季风期，占印度全国总降水量的大约80%。而印度农业分别占全国就业总量的54%和GDP的19%以上，因此在干旱或洪涝年份，降水分布的任何变化都会对印度农业产生极大影响。随着人口增长，农产品需求大幅增加，但农业用地却十分有限。气候变化和极端天气气候事件（如干旱和洪水等）与社会、经济等因素一起，对印度农业产生了极其重大的影响。 依据农业气候特征，印度被划分为六个区，分别是山区、副热带湿润区、热带干旱区、热带湿润区、半干旱区和干旱区。副热带湿润区（HSTC）从北方的旁遮普邦一直延伸至东部的西孟加拉邦，极端天气气候事件发生的概率在该区域也更高。此外，该区域的大部分为印度-恒河平原（IGP），这是一个包括巴基斯坦、印度北部和东部部分地区、孟加拉国和尼泊尔的广阔地区。印度-恒河平原仅占印度国土面积的13%，但该区域的粮食产量占全国总产量的50%，并且养活了40%的人口。包括印度-恒河平原在内的副热带湿润区，对极端天气气候事件，尤其是干旱和洪水，是极端脆弱的。本论文分为四个章节，包括（a）使用粮农组织对印度农业的统计数据，估计印度农业用地总需求量，（b）使用SPEI全球数据集，分析印度（尤其是副热带湿润区）干旱的时空特征及其在夏季（4-9月）对农业的影响，（c）使用两种不同情景下的CMIP5模式数据，研究副热带湿润区极端干旱/洪涝事件的历史变化和未来预估，估算了降水和地表温度变化的相应作用。最后，（d）利用CESM1.1集合数据，量化了自然和人为因子在副热带湿润区历史和未来温度变化趋势中的相对贡献。 1.1 印度农业用地的历史变迁: 社会经济和极端气候因素的作用印度是人口众多、经济迅速增长和自然资源有限的发展中国家之一, 因此面临着粮食安全的巨大压力。在本章中, 我们估算了1961年-2009年印度农业土地需求的历史变化。一个国家的土地需求是由人口、人均消费/饮食、技术增长和气候因素决定的。首先, 我们量化了社会经济因素对农业土地需求的作用。这里, 在以下框架下进行了讨论并比较了我们的结果： 将不同食物品种的消费与饮食模式联系起来;然后, 在人口迅速增长、经济改革导致的饮食多样化和城市化对印度粮食安全施加极大压力的情况下, 与农业总土地需求联系起来。我们还阐述了技术传播的作用, 并批判地分析了政府政策的成就和缺点,来确保国家粮食自给和粮食安全。研究结果显示, 1961-2009年间土地总需求量约增加 42%, 而人均土地需求则显著下跌约48%。此外, 我们的研究表明, 人口增长占印度土地需求总量增长的绝大部分。因此, 对农业土地资源的可持续性管理是印度急需的, 因为需要更多的粮食来满足庞大人口的饮食需求。除社会经济因素外, 气候变化和极端气候事件 (如干旱、洪水等) 对印度农业和土地资源影响极大。在极端干旱事件期间, 由于印度夏季季风减弱, Kharif地区粮食 作物产量大幅度下降。 1.2 干旱对印度恒河平原副热带湿润区农业的影响在本研究中, 我们研究了印度干旱的时空特征及其在夏季（4-9月）对农业的影响。研究中 我们使用了1982-2012年间六个月时间尺度的标准化降水蒸散指数 (SPEI) 数据集。以 SPEI<–1为标准, 我们得到了干旱发生频次的分布图, 并发现包括印度-恒河平原在内的副热带湿润区干旱发生的频率高达40–45%。副热带湿润区对印度年度谷物产量的贡献超过50%。该区域不仅干旱发生频率升高，整个地区在近几十年来变得越来越干旱。此外，HSTC 地区的谷物产量在2000年之后呈现逐渐降低的趋势，这与受干旱影响区域从2000年之前的占比20–25%上升至2000年之后的50–60%是一致的。谷物产量和干旱影响区域变化之间较高的相关系数 (-0.69) 也证实, 至少50% 的农业 (谷类) 减产损失与干旱有关。在分析降水和地表温度异常对 SPEI 的影响时, 发现在 HSTC 区的表面温度对降低 SPEI 起主要作用。HSTC区地表温度上升与SPEI之间极强的负相关也进一步证实了这种联系。更高的温度会导致更多的蒸发和干燥, 因此近几十年来受干旱影响的地区也扩大了。由于 HSTC 区对农业具有十分重要的意义,且在极端气候事件面前十分脆弱, 因此研究未来该地区极端气候事件的变化是十分重要的。 1.3 使用CMIP5模式结果对印度-恒河平原副热带湿润区- 未来极端气候事件的预估印度自60年代以来在夏季季风期经历了一系列极端干旱和洪水事件。包括印度-恒河平原（IGP）地区在内的副热带湿润区（HSTC区）,在极端气候事件中极其脆弱。然而, 以前的研究很少关注印度，尤其是IGP地区在全球变暖背景下的极端干旱和洪涝事件的未来变化,而这对于提前制定农业应对措施、水资源管理、人类健康等至关重要。在气候发生重大变化的背景下, 还很少对印度尤其是IGP地区极端气候事件的未来变化进行全面评估,这也是本研究的主要动机。基于CMIP5试验中对历史的模拟和不同变暖情景下（RCPs）的模拟结果，能够对HSTC区在未来极端气候事件的变化有更深入的理解。大气环流模型（GCMs）是预估未来气候变化预测的主要工具之一。而不同的RCPs情景是由各类社会经济和技术发展的不同情景所导致的每一个辐射强迫因子的变化综合起来决定的。因此, 我们研究了干旱/洪涝的历史变化以及在 CMIP5的两种不同情景下, 对极端事件的未来变化进行了预估。首先, 基于观测数据对模式中的降水（P）和温度（T）等参数进行了校正, 并最终选取了与观测数据同位相的六个模式。接下来, 我们计算了潜在蒸散发量（PET）和标准化潜在蒸散发指数 (SPEI) 来表征极端事件。HSTC 区的P 和 PET 在未来均表现为增加；然而洪涝和干旱在未来都表现为持续增长。相对来说, P 在 IGP 区域 (洪涝情况)比 PET 增加快, 并且在该区域的南部和东部地区 (干旱条件) 下降。在 RCP8.5情景下， 降水增加导致的缓解效应（RCP4.5情景）被增强的PET和明显的干旱极端事件所抵消。这些特征与多模式平均的 SPEI 的增加/减小相吻合, 也符合 P?PET的空间分布。在 RCP4.5 和 RCP8.5 方案下, 受到干旱和洪涝影响的地区都增多了。我们的结果清晰地表明地表温度的升高在未来印度的极端事件中，尤其是干旱事件中，扮演着越来越重要的角色。然而, 数十年来区域气温变化的驱动机制尚未分析；未来变化趋势究竟是受自然变化或（和）人为强迫的影响仍需要进一步的研究。1.4印度夏季地表气温的年代际变化 (SAT): 自然变化和外部强迫的作用这项研究强调了印度次大陆局地或区域尺度上夏季 (JJA) 地表气温在历史时期 (1961–2000) 和未来 (2010–2060) 变化趋势中内部变率和外部强迫的相对重要性。这里我们使用了地球系统模型的Large Ensemble试验 (CESM-LE) 数据 (35个 成员) 在考虑内部气候变率的情况下评估历史和未来的气候变化 (1920–2100)。每次试验都使用相同的人为辐射强迫 (例如, 温室气体的增加), 但设置略微不同的初始大气状态。因此, 每个模式集合中历史和预估的温度趋势差异全是由于固有的、不可预知的气候系统内部变率。HSTC区域（包括IGP区域）夏季 (JJA) 历史时期的SAT总趋势表现为增强的冷却 ( = 4°C)。温度总趋势由外部强迫和内部变率构成。前者导致的在HSTC区（包括IGP区域）的冷却和增暖趋势分别为 ?3°C 和 ~ 2°C。另一方面, 自然气候变率在印度地区同时出现了降温和升温的趋势, 这对使用气候模式预估未来变化引入了极大的不确定性。 在历史时期, 印度区域信号和噪音的比值(信噪比,即强迫变率和自然变率的比值) 小于1, 表明内部气候变率占主导地位。另一方面, 对未来数十年的预估表现为升温趋势, 信噪比远高于1。我们的分析表明, 自然或内部变率的相对贡献极大地掩盖了印度地区的升温趋势,即使在 RCP8.5情景下也是如此。 |
| 英文摘要 | In the recent decades, India experiences a series of extreme drought and flood events during the summer months. For countries like India, where the rainfall is seasonal in nature, agriculture is mostly rain-fed. The maximum rainfall occurs during the summer monsoon months (June-September), and it accounts approximately 80% of the total annual rainfall of the country. Therefore, any shift in normal rainfall during the drought and flood years, has significant impact on the agricultural sector of the country, which accounts more than 54% and 19% of gross national employment and GDP, respectively. Although demand increases significantly due to population growth, but the agricultural land for food production is limited. Along with the socio-economic factors, climate change and extreme events (e.g. drought, flood etc.) have significant impact on the Indian agriculture.Based on the agro-climatic zones, India is divided into six major divisions, e.g. Montane, Humid Subtropical, Tropical dry, Tropical wet, Semi-arid and Arid zones. Geographically, the humid subtropical climatic (HSTC) zone is stretching from Punjab in the North to the West Bengal in the East and the probability of extreme events is higher in this region. Furthermore, a greater part of the HSTC zone comprises the Indo-Gangetic Plain (IGP), an area encompassing the wider region of Pakistan, northern to eastern part of India, Nepal and Bangladesh. The IGP region covers nearly 13% of the country’s total geographical area, and it yields about 50% of the total food grain to feed 40% of the population of the country. The HSTC region, which includes the IGP region, is highly vulnerable to the climatic extremities, particularly drought and flood.The present thesis is divided into 4 working chapters, which include (a) the estimation of total agricultural land requirement for food in India; using FAO based agricultural statistics data over India, (b) investigate the spatio-temporal characteristics of drought in India (particularly HSTC zone) and its impact on agriculture during the summer season months (April–September), using the Standardized Precipitation Evapotranspiration Index (SPEI) global datasets, (c) investigate the historical variation in dry/wet events and project the future changes in extreme events under two different scenarios of the CMIP5 models in the HSTC zone. The relative roles of precipitation and surface temperature change are estimated. Finally, (d) we have quantified the relative contribution of the natural and the anthropogenic factors, driving the historical and future temperature trend over the HSTC zone, using CESM1.1 multi-member ensemble datasets. 1.1 Historical changes in the agricultural land requirement in India: Role of socio-economic and extreme climatic factors India is one of the rapidly developing countries with huge population, rapid economic growth and limited natural resources, therefore, facing massive pressure of food security. In this chapter, we estimate the historical changes in agricultural land requirement in India from 1961 to 2009. The land requirement of a country is a function of population, per capita consumption/diet, technological growth and climatic factors. In the beginning, we have quantified the role of socio-economic factors on the agricultural land demand. Here we discuss and compare our results in a framework which links consumption of different groups of food items to diet pattern; then to the total land requirement for food in a scenario when population is growing rapidly and diet diversification and urbanization due to economic reform impose excessive pressure on food security of India. We also elaborate the role of technology dissemination and critically analyze the achievements and drawbacks of the government policies to ensure the food self-sufficiency and food security of the nation. Our results show that the total land requirement increases approximately by 42%, whereas per capita land demand decreases significantly by around 48% from 1961 to 2009. Furthermore, our studies reveal that population growth dominates most of the increase in total increase in land requirement for India. Therefore, sustainable management of agricultural land resource is an urgent need for India as there will be demand for more food to meet the diet requirement for the entire population. Apart from the socio-economic factors, climate change and extreme climate events (e.g. drought, flood etc.) have significant impact on the Indian agriculture and land resources. We have seen a significant decrease in Kharif crop production due to weakening of the Indian summer monsoon during the extreme drought events. 1.2 Impact of drought on agriculture in the Humid Subtropical Indo-Gangetic Plain, IndiaIn this study, we investigate the spatio-temporal characteristics of drought in India and its impact on agriculture during the summer season months (April to September). For our analysis, we used the Standardized potential Evapotranspiration Index (SPEI) datasets between 1982 and 2012 at 6 month timescale. Based on SPEI<–1 criteria, we obtain the number of occurrences of drought map and have found that the Humid Subtropical Climatic zone (HSTC), which include the Indo-Gangetic Plain region of India is highly drought prone with an occurrence frequency of 40–45%. Moreover, in the recent decades the frequency of occurrence of drought has increased over the HSTC region. This region contributes at least 50% of India’s annual cereal production. Moreover, the cereal production in the HSTC region experienced a gradual declining trend from 2000 onwards, which is consistent with the increase in drought affected areas from 20–25% to 50–60%, before and after 2000, respectively. Higher correlation coefficient (-0.69) between the changes in cereal production and drought affected areas, confirms that at least 50% of the agricultural (cereal) losses is associated with drought. While analyzing individual impact of precipitation and surface temperature anomalies on SPEI (6), we found that in the HSTC region surface temperature plays the primary role in lowering of SPEI. The linkage is further confirmed from the correlation analysis between the SPEI (6) and surface temperature rise, which exhibits strong negative values in the HSTC region. Higher temperature may cause more evaporation and drying, which therefore increases the area affected by drought in the recent decade. Since the HSTC region is highly significant for agriculture and vulnerable to the climatic extremities, it is essential to investigate future changes in extreme climate events over this region. 1.3 CMIP5 multi-model projections of extreme climate events in the Humid Subtropical Indo-Gangetic Plain, IndiaSince 1960’s, India experiences a series of extreme drought and flood events during the summer monsoon months. The HSTC zone, which comprises the Indo Gangetic Plain (IGP) region of India, is highly vulnerable to the climatic extremities. However, very few of the previous studies had focused on the future changes of extreme dry and wet events in India and none in the IGP region under global warming, which is crucial to advance planning for agricultural adaptation, water resource management, human health etc. Under the background of significant climate change, a comprehensive evaluation of future changes in extreme climate events in the IGP region of India has not yet been performed and is the primary motivation for this study. A better insight into the future changes in the extreme events over the HSTC zone can be achieved based on historical simulations and the newly developed representative concentration pathways (RCPs) under the Coupled Model Inter-comparison Project 5 (CMIP5). General Circulation Models (GCMs) are one of the primary tools for deriving projections of future climate change. RCPs represent pathways of radiative forcing based on the concept that any single radiative forcing pathway can result from a diverse range of socioeconomic and technological development scenarios.Therefore, we investigate the historical variation in dry/wet conditions and project the future changes in extreme events under two different scenarios of the CMIP5 models. Firstly, the model parameters i.e. precipitation (P) and temperature (T) are bias corrected with respect to observation data and finally 6 models are selected, which are in right phase with the observation for composite analysis. Next, we calculate the potential evapo-transpiration (PET) and the Standardized Potential Evapo-transpiration Index (SPEI) to characterize the extreme events. Both P and PET are projected to increase in the HSTC zone; however, both the wet and dry conditions demonstrate a persistent increase in future. In relative terms, P increases faster than PET along the IGP region (wet condition) and decreases in the southern and eastern part of the region (dry condition). The mitigating effect (RCP4.5 scenario) of precipitation increase will be overridden by strengthened PET and extreme dry condition project markedly under RCP8.5 scenario. The features are consistent with the increase/ decrease in multi-model mean SPEI, consistent with the spatial pattern of P?PET. The area affected due to wet and dry events will be relatively higher under the RCP4.5 and RCP8.5 scenario, respectively. Our result clearly indicates the increasing role of surface temperature rise, for the future changes in extreme events, particularly dry events over the Indian region. However, the mechanism driving the multi-decadal regional temperature change is not yet investigated; whether the natural variability and/or the anthropogenic forcings are contributing the trends need to be understood. 1.4 Multidecadal changes in summer surface air temperature (SAT) in India: Role of natural variability and external forcings This study highlights the relative importance of internally generated versus externally forced trends in summer (June–August) surface temperature change over the historical (1961–2000) and future (2010–2060) periods, at local or regional scales over the Indian subcontinent. Here we have used the Community Earth System Model Large Ensemble (CESM-LE) data (35 members) to assess the historical and near-future climate change (1920–2100) in the presence of internal climate variability. Each of the runs are subject to identical anthropogenic radiative forcing (e.g., greenhouse gas increase) but begins from a slightly different initial atmospheric state. Thus, the diversity of the historical and the projected temperature trends within each model ensemble is solely due to the intrinsic, unpredictable variability of the climate system. The summer (JJA) SAT total trend during the historical period exhibit an amplified cooling (= 4°C) is projected in all the ensemble members under the RCP8.5 scenario. The total trend is partitioned into contributions from the externally forced response and the internal variability. The former displays a cooling and a warming trend with maximum amplitudes of approximately <= ?3 °C and ~ 2°C, respectively in the HSTC zone (include the IGP). On the other hand, the natural climatic variability exhibits both the cooling and the warming trend over the Indian region and it introduces a wide range of uncertainty to the future projection in the climate models. For the historical period, the signal to noise ratio (SNR i.e. ratio of forced and natural variability) is less than 1, over the Indian region, which indicates that the internal climatic variability dominates over the forced response. On the other hand, a warming trend is projected during the future decades and the SNR is much higher than 1. Our analysis indicates that, the relative contribution of the natural or internal variability masked the warming trend over the Indian region, to a greater extent, even under the RCP8.5 warming scenario. |
| 中文关键词 | \印度\ ; \极端气候事件\ ; \CMIP5模式预估\ ; \内部气候变率\ ; \外强迫\ |
| 英文关键词 | \India\ \Extreme climatic events\ \CMIP5 model projection\ \internal climatic variability\ \external forcings\ |
| 语种 | 中文 |
| 国家 | 中国 |
| 来源学科分类 | 气象学 |
| 来源机构 | 中国科学院大气物理研究所 |
| 资源类型 | 学位论文 |
| 条目标识符 | http://119.78.100.177/qdio/handle/2XILL650/287856 |
| 推荐引用方式 GB/T 7714 | RESHMITA NATH. 干旱对印度农业的影响及CMIP5对印度极端气候的预估[D]. 中国科学院大学,2017. |
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