Evolving Threshold of Flood-Leading Precipitation in a User-Oriented Forecast System Based on the TIGGE Dataset

Specific users play a key role in interactive forecast systems through user-oriented information (UOI). For hydrological users, a key component of the user-oriented forecast system (UOFS) is to determine the threshold of flood-leading precipitation (TFLP) as a target of the forecast by considering the decision-making information at the user end. This study demonstrates a novel way of simulating TFLP via the inverse simulation of a hydrological model, combined with the flood hazard assessment in the upper reaches of the Huai River Basin controlled by the Wang Jiaba (WJB) hydrological station. The flood hazard, defined as the probability of precipitation beyond the daily evolving TFLP for the next day, was evaluated by using the THORPEX Interactive Global Grand Ensemble (TIGGE) datasets, including 162 members retrieved from 5 TIGGE archive centers. Having integrated the real-time monitored water level (as the UOI) into the UOFS, we applied it to the flood season of 2008 as a case study to evaluate the flood hazard generated by the UOFS for the WJB sub-basin. The simulated TFLP corresponded well with the gap between the monitored and warning water level. The predicted flood hazard probability showed good agreement with the first two flood peaks at 100% accuracy, while exceeding 60% accuracy for the third flood event in that season. Thus, the flood hazard could be better quantified via integration of the forecasted flood-leading precipitation. Overall, this study highlights the usefulness of a UOFS coupled with interactive UOI of real-time water level to determine the dynamical TFLP for flood hazard evaluation with ensemble precipitation forecast. The early flood warning which resulted from such integrated UOFS is directly applicable to operational flood prevention and mitigation.

Weather Forecast Semiotics: Public Interpretation of Common Weather Icons

Weather icons are some of the most frequently used visual tools meteorologists employ to communicate weather information. Previous research has shown a tendency for the public to make inferences about weather forecast information based on the icon shown. For example, people may infer a higher likelihood of precipitation, assume a higher intensity of precipitation, or determine the duration of expected precipitation if the weather icon appears to show heavy rain. It is unknown to what extent these inferences align with what the meteorologist who chose the icon intended to convey. However, previous studies have used simulated weather icons rather than ones currently in use. The goal of our study was to explore how members of the public interpret actual weather icons they see on television or in mobile applications. An online survey distributed by broadcast meteorologists through social media was used to collect 6,253 responses between August and September of 2020. Eleven weather icons currently used by broadcast meteorologists were included in the study. We also tested eight common weather phrases and asked people whether they thought the icons were good illustrators of those phrases. Additionally, people were asked to assign a probability of precipitation (PoP) to the icons. The findings of our study offer new and unique insights that will improve the communication of weather information by giving meteorologists information about how their audiences interpret weather icons.

Smaller land-sea contrast on probability of precipitation (POP) of warm clouds over globe

<p>Proper observation of global warm rain and understanding of its formation processes can significantly advance our understanding on aerosol-cloud-precipitation interactions. Previous study shows that due to smaller cloud effective radii (Re), rain from liquid clouds over land is sharply reduced compared to oceans (Mülmenstädt, 2015). However, in our study, we use A-Train satellite observations to show that there should be smaller land-sea difference on probability of precipitation (POP) of warm clouds between land and oceans. The discrepancy is probably because the algorithm bias in CloudSat precipitation flag products over land, which may mistakenly treat drizzle as no rain. We also find that if Re is smaller than 14 mm, no matter how thick the warm cloud is it can hardly produce significant precipitation (here defined as radar reflectivity factor lager than 0dBZ), which can generate dynamic feedback on the development of clouds.</p>

Areal Probability of Precipitation in Moist Tropical Air Masses for the United States

Moist tropical (MT) air masses routinely host convective precipitation, including weakly forced thunderstorms (WFTs). These short-lived, isolated events present recurring forecasting challenges due to their spatially small footprints and seemingly erratic behavior in quiescent warm-season environments worldwide. In particular, their activity is difficult to accurately characterize via probability of precipitation (POP), a common forecast product for the general public. This study builds an empirical climatological POP distribution for MT days over the continental United States using Stage IV precipitation estimates. Stage IV estimates within MT air masses between May–September (i.e., the boreal warm season) 2002–2019 are masked into precipitation (≥0.25 mm) and nonprecipitation (<0.25 mm) areas and standardized by the number of MT days. POPs are higher when MT air masses are present. For the Southeast U.S., POP generally increases ~15% compared to the overall warm-season value. At 1800 UTC (1–2 PM LT) daily, POPs are confined to coastal areas and east-facing ridges, and advance inland by 2100 UTC (4–5 PM LT). Climatologically, ~50% of the warm-season precipitation in the Southern U.S. occurred in MT environments. This study emphasizes the need for better forecasting tools and climatological analyses of weakly forced environments.

Modifying the Extended Forecast Graphic to Improve Comprehension

The extended forecast graphic (EFG) is a popular graphic used by meteorologists to convey weather information, but it is poorly understood by the public. Deficiencies in the format, content, and presentation of the EFG contribute to a decrease in the efficacy of this graphic and reduce the comprehension of weather information. The format of the EFG has largely gone unchanged since the graphic first became popular more than four decades ago. The goal of this research was to modify the format of the existing EFG to address current limitations that inhibit understanding and create confusion among the public. Data were gathered from an online survey of the public (n = 885). Four modified versions of the EFG were developed, evaluated, and compared with the existing EFG. Removing probability of precipitation (PoP) information, reducing the number of days shown, and switching to a horizontal layout featuring timing and intensity information resulted in higher percentages for comprehension of weather information and positive comments when compared with the current version. A majority of participants responded that forecasters could accurately predict the weather 3 days out, providing justification for the reduction in number of days shown in the modified EFGs. Results suggest that agencies and members of the meteorological community should continue evaluating and discussing the most effective ways to use graphics to convey weather information to their audiences.

Hydropower impact on the river flow of a humid regional climate

Land use and water management have considerable impacts on regional climates. This paper proposes that in humid regions with low wind patterns the construction of hydropower storage reservoirs contributes to the increases in the probability of precipitation in the regional climate. This observation has been tested with a methodology that calculates the cumulative influence of reservoir construction in the basins surrounding with a proposed index named Cumulative Impact of Existing Reservoirs, and compares this index with the historical flow of the rivers. It was found that the construction of reservoirs in Brazil had a considerable impact on its river flows.

Changing Probabilities of Days with Snow and Rain in the Atlantic Sector of the Arctic under the Current Warming Trend

Trends in the probabilities of days with liquid, solid, and mixed precipitation are discussed on annual and intra-annual scales along with their relationship to air temperature in the Atlantic sector of the Arctic. Data on weather phenomena were used to identify precipitation phases. The data cover various periods but all series extend to 2017. Trends in the annual air temperature and probability of precipitation phases for various long-term periods are discussed and differences in the mean air temperature and probability of precipitation phases between 1979–97 (insignificant warming) and 1999–2017 (significant warming) on an intra-annual scale. In the studied region, the precipitation phases were sensitive to warming and atmospheric circulation to various degrees, depending on the phase, mean climate, month, and local conditions. The probability of days with rainfall increased (by +1% to +3% per decade), whereas the probability of days with snowfall decreased (by −1.5% to −2.4% per decade). The increasing trends in the probability of rainy days at all stations and decreasing trends in the probability of snowy days in the southern part of the region were warming induced. The most significant and widespread trends in snowy and rainy days were found in September. The probability of days with mixed precipitation exhibited no trends due to an inverse reaction to warming in the warmer and colder parts of the year. Temporal variability in the probability of precipitation phases was significantly linked to three teleconnection patterns playing a role in various parts of the year.

Analysis on sub-daily characteristics of one hour precipitation based on observed data

&lt;p&gt;In order to reveal sub-daily characteristics of precipitation, this study analyzes statistical characteristics of hourly precipitation by using statistical methods. The hourly precipitation observed data was collected from 34 representative precipitation stations of Sichuan Province of China during 2001-2007. The results show that the average one hour precipitation is 0.148 mm, and the probability density function of precipitation intensity y = 0.2235e-0.083x. The average daily precipitation time is 2.6 hours, and the probability of precipitation event each hour follows a sine wave. As well as the maximum probability time when precipitation occurs in a day is 3 AM to 4 AM, and the minimum probability time is 14 PM to 15 PM. It suggests a method for precipitation downscaling from daily into hourly.&lt;/p&gt;

Ecological-economically balanced functioning of combined drainage systems on heavy soils Novgorod region

The article deals with the ecological and economically balanced functioning of combined drainage systems on heavy soils of the Novgorod region. The water-air regime of the drained lands and the parameters influencing it (a drainage drain, a level of ground waters) is considered as an ecological indicator, and economic – increase of productivity of lands. The studies were carried out at the experimental experimental field, drained by closed drainage with backfilling of the drainage trench of the sand-gravel mixture to the arable horizon (control), two-tier drainage and a combination of with deep loosening. The analysis of the results of the study showed that the experimental combined drainage system was set aside 88% more runoff compared with control; in the excessively wet growing season (25% probability of precipitation), the system of two-tier drainage there was the lowest level of groundwater and soil moisture; the effect of deep loosening began to decrease by 3 year of operation of combined drainage, so it is recommended to carry out deep loosening on loamy soils every 3 years; from the ecological and economic point of view the most balanced option is the combined two-tier drainage.

Perception and Comprehension of the Extended Forecast Graphic: A Survey of Broadcast Meteorologists and the Public

There have been multiple efforts in recent years to simplify visual weather forecast products, with the goal of more efficient risk communication for the general public. Many meteorological forecast products, such as the cone of uncertainty, storm surge graphics, warning polygons, and Storm Prediction Center (SPC) convective outlooks, have created varying levels of public confusion resulting in revisions, modifications, and improvements. However, the perception and comprehension of private weather graphics produced by television stations has been largely overlooked in peer-reviewed research. The goal of this study is to explore how the extended forecast graphic, more commonly known as the 7, 10 day, etc., is utilized by broadcasters and understood by the public. Data were gathered from surveys with the general public and also from broadcast meteorologists. Results suggest this graphic is a source of confusion and highlights a disconnect between the meteorologists producing the graphic and the content prioritized by their audiences. Specifically, timing and intensity of any precipitation or adverse weather events are the two most important variables to consider from the viewpoint of the public. These variables are generally absent from the extended forecast graphic, thus forcing the public to draw their own conclusions, which may differ from what the meteorologist intends to convey. Other results suggest the placement of forecast high and low temperatures, use of probability of precipitation, icon inconsistency, and length of time the graphic is shown also contribute to public confusion and misunderstanding.