COVID-19是由新型冠状病毒SARS-CoV-2所引发的传染病，引发了前所未有的公众健康危机。评估气象因素如何影响SARS-CoV-2的传播，对COVID-19疫情防控有重要意义。COVID-19大流行使全球经济前景面临着巨大的不确定性。量化COVID-19疫情造成的经济损失与疫情防控措施之间的关系，采取科学合理的防控措施，有助于以较小的经济代价控制疫情。本文以COVID-19的“天气条件-疫情传播-经济损失”为主线开展研究，主要研究内容和创新点如下。

     (1) 天气条件对COVID-19疫情传播的影响分析。通过耦合Penman-Monteith公式和Kelvin公式，本文估算了携带着SARS-CoV-2病毒的液滴在一定天气条件下的蒸发时间。研究结果表明，携带着SARS-CoV-2病毒的液滴的蒸发时间在昼夜分布、地域分布和时空分布上存在着很大的差异性。在日落到深夜期间 (18:00 ~ 1:00)，携带着SARS-CoV-2病毒的液滴的平均蒸发时间更长，尤其是在热带地区，这意味着通过液滴传播的风险较高。研究结果建议，在日落到深夜期间应尽可能地减少社交活动，以降低液滴传播的风险，尤其是在热带地区。本研究中携带着SARS-CoV-2病毒的液滴的蒸发时间，可以作为一项具有物理机制的风险评估指标，用以评估COVID-19疫情传播的综合风险。

     (2) COVID-19疫情在不同防控措施下造成的经济损失分析。通过耦合五段SE^PAI^QHR模型和经济损失模型，本文估算了武汉地区COVID-19疫情在不同防控措施下的经济损失。使用了两个参数（ r 和 g ）对防控措施进行参数化： r 为有效接触人数，表示社会疏离的程度； g 为阳性患者的平均等待时间，表示病人能否及时得到隔离和治疗。研究结果表明，经济损失在参数 r=5 ~ 6 人附近存在一个“中央谷”，且经济损失随着参数 g 的减小而减少。研究结果建议，应尽早地实施严厉的疫情防控措施，包括人群之间的社会疏离和对阳性患者的及时隔离救治，这样能以较小的经济代价遏制疫情蔓延。

    COVID-19 is an infectious disease caused by a novel coronavirus SARS-CoV-2, which has caused an unprecedented public health crisis. Analyzing which natural factors affect SARS-CoV-2 transmission is meaningful to COVID-19 prevention and control. With the COVID-19 pandemic spreads, the global economic outlook faces enormous uncertainty. Quantifying the relationship between economic losses caused by COVID-19 and control measures can help controlling the epidemic with a small economic cost. This dissertation focuses on the “weather conditions – epidemic spread – economic losses” of COVID-19. The main research content and novel contribution are described below.

     (1) Analysis of the impact of weather conditions on COVID-19 transmission. By coupling the Penman-Monteith equation and the Kelvin equation, the evaporation time of SARS-CoV-2 virus-laden droplets under local weather conditions was estimated. The results showed that the evaporation time of SARS-CoV-2 virus-laden droplets varies greatly in the diurnal, geographical, and spatiotemporal distributions. Between sunset and late-night (18:00 ~ 1:00), the average evaporation time of SARS-CoV-2 virus-laden droplets is longer, especially in tropical regions, which means a higher risk of droplet transmission. These findings suggest that social distancing between sunset and late-night can possibly reduce the risk of droplet transmission, especially in tropical regions. The evaporation time of SARS-CoV-2 virus-laden droplets can be used as a risk assessment index with a physical mechanism to assess the comprehensive risk of COVID-19 transmission.

     (2) Analysis of economic losses caused by COVID-19 under different prevention and control measures. By coupling the five-stage SE^PAI^QHR model and the economic loss model, economic losses caused by COVID-19 in Wuhan under different prevention and control measures were estimated. The prevention and control measures were parameterized into two parameters (r andg ), wherer is the effective number of daily contacts, representing the degree of social distancing; whereg is the average waiting time for quarantined patients, representing whether the patients can be isolated and treated in time. The results showed that there is a “central valley” in economic losses near the parameterr=5~6 people, and it decreased as the parameterg decreased. These findings suggest that stringent prevention and control measures, including social distancing and timely isolation and treatment, should be implemented as soon as possible in order to curb COVID-19 transmission at a small economic cost.