# Passive Microwave Imagers, Their Applications, and Benefits: A Review
## 1 Introduction

Table 1: Summary of past, current, and future satellite PMWIs [13]. continue the legacy of PMWI technology. These future missions are poised to provide even more comprehensive data, enhancing the ability to monitor and predict weather and climate phenomena [31; 32; 33]. Consistent and accurate PMWI products are essential for advancing the understanding of Earth's atmospheric and surface processes, improving weather forecasting, climate monitoring, and environmental research. Furthermore, these advancements yield significant societal benefits, including improved observation of rain and snow, more reliable winter weather forecasts, better flood and wildfire management, sustainable marine resource monitoring, and enhanced tracking and prediction of Tropical Cyclones (TCs) [34; 35; 36; 37; 38; 39]. PMWI products complement Infrared (IR) retrievals by providing unique insights into atmospheric moisture profiles, precipitation, and surface characteristics under cloud-covered conditions where IR methods may have limitations. Despite their importance, challenges such as inconsistencies in data usage, limited accessibility, and gaps in the literature limit their broader application. Understanding these issues is important to fully realize the potential impacts of PMWI data in areas such as agricultural management, industrial operations, disaster preparedness, and resilience planning. As a result, this review, along with a survey, was conducted by the Center for Hydrometeorology and Remote Sensing (CHRS) at UC Irvine in collaboration with expert users and the general public. It provides an analysis of the relevance, applications, and societal implications of PMWI data, highlighting their critical role in meteorological and hydrological applications. Additionally, it offers valuable insights into the current usage, limitations, impacts, and potential improvements for PMWI data. By identifying key areas for improvement, this review aims to guide future developments and investments in PMWI technologies, ensuring their sustained value for both scientific advancements and society. The rest of this review discusses the applications and benefits of PMWI technology, particularly in the context of its societal impacts. It highlights the historical development and advancements of PMWIs, emphasizes their critical roles in environmental monitoring and disaster management, and presents findings from a recent survey that capture the perspectives of expert users and the general public. By examining these aspects, this review seeks to underscore the importance of PMWIs in improving weather forecasting, climate monitoring, and the overall understanding of atmospheric and surface processes, while also addressing the limitations and potential improvements for future implementations. The remainder of this paper is structured as follows: Section 2 explores PMWI applications and impact areas, covering various aspects such as applications and benefits, including TCs and hurricanes, global precipitation and extreme events, fire severity and carbon emissions, Numerical Weather Prediction (NWP), the cryosphere, sea surface conditions, and soil moisture and drought. It also examines the impact areas of PMWIs within the National Weather Service (NWS). Section 3 discusses the applications, benefits, and societal impacts of PMWIs. This paper then summarizes key findings from the survey and related discussions in Section 4. Finally, the conclusion, Section 5, highlights the main insights and suggests directions for future research.