Sustained wind forcing and water level anomalies in Annapolis, MD

Like many coastal communities throughout the Mid-Atlantic region, relative sea level rise and accelerating instances of coastal nuisance flooding are having a tangible negative impact on economic activity and infrastructure in Annapolis, MD. The drivers of coastal nuisance flooding, in general, are a superposition of global, regional, and local influences that occur across spatial and temporal scales that determine water levels relative to a coastal datum. Most of the research to date related to coastal flooding has been focused on high impact episodic events, decomposing the global and regional drivers of sea level rise, or assessing seasonal to interannual trends in. In this study, we focus specifically on the role of short-duration (hours) meteorological wind forcing on water level anomalies in Annapolis, MD. Annapolis is an ideal location to study these processes because of the orientation of the coast relative to the prevailing wind directions, and the long record of reliable data observations. Our results suggest that three-, six-, nine-, and twelve-hour sustained wind forcing significantly influences water level anomalies in Annapolis. Sustained wind forcing out of the northeast, east, southeast and south is associated with positive water level anomalies, and sustained wind forcing out of the northwest and north is associated with negative water level anomalies. While these observational results suggest a relationship between sustained wind forcing and water level anomalies, a more robust approach is needed to account for other meteorological variables and drivers that occur across a variety of spatial and temporal scales.

Upper Gila, Salt, and Verde Rivers: Arid Land Rivers in a Changing Climate

The major tributary of the Lower Colorado River, the Gila River, is a critical source of water for human and natural environments in the Southwestern US. Warmer and drier than the Upper Colorado River basin (UCRB), with less snow, and a bi-modal precipitation regime, the Gila River is controlled by a set of climatic conditions that is different from the controls on Upper Colorado River flow. Unlike the Colorado River at Lees Ferry, the Upper Gila River and major Gila River tributaries, the Salt and Verde Rivers, do not yet reflect significant declines in annual streamflow, in spite of warming trends. Annual streamflow is dominated by cool season precipitation, but the monsoon influence is discernable as well, variable across the basin and complicated by an inverse relationship with cool season precipitation in the Salt and Verde River basins. Major multi-year streamflow droughts in these two basins have frequently been accompanied by wet monsoons, suggesting that monsoon precipitation may partially offset the impacts of a dry cool season. While statistically significant trends in annual streamflow are not evident, decreases in fall and spring streamflow reflect warming temperatures and some decreases in spring precipitation. Because climatic controls vary with topography and the influence of the monsoon, the impacts of warming on streamflow in the three sub-basins is somewhat variable. However, given relationships between climate and streamflow, current trends in hydroclimate, and projections for the future, it would be prudent to expect declines in Gila River water supplies in the coming decades.

Complex effects of telecouplings on forest dynamics: an agent-based modeling approach

Rural areas are increasingly subject to the effects of telecouplings (socioeconomic-environmental interactions over distances) whereby their human and natural dynamics are linked to socioeconomic and environmental drivers operating far away, such as the growing demand for labor and ecosystem services in cities. Although there have been many studies evaluating the effects of telecouplings, telecoulplings in those studies were often investigated separately and how telecoulplings may interact and affect dynamics of rural coupled human and natural systems (CHANS) jointly was rarely evaluated. In this study, we developed an agent-based model and simulated the impacts of two globally common telecouplings, nature-based tourism and labor migration, on forest dynamics of a rural CHANS, China’s Wolong Nature Reserve (Wolong). Nature-based tourism and labor migration can facilitate forest recovery, and the predicted forest areas in Wolong in 2030 would be reduced by 26.2 km2 (6.8%) and 23.9 km2 (6.2%), respectively, without their effects. However, tourism development can significantly reduce the probability of local households to have member(s) out-migrate to work in cities and decrease the positive impact of labor migration on forest recovery. Our simulations show that the interaction between tourism and labor migration can reduce the potential forest recovery by 3.5 km2 (5.0%) in 2030. Our study highlights that interactions among different telecouplings can generate significant impacts on socioeconomic and environmental outcomes and should be jointly considered in the design, management, and evaluation of telecouplings for achieving sustainable development goals.

Weather Factors Associated with Extremely Large Fires and Fire Growth Days

Abstract“Megafires” are of scientific interest and concern for fire management, public safety planning, and smoke-related public health management. There is a need to predict them on time scales from days to decades. Understanding is limited, however, of the role of daily weather in determining their extreme size. This study examines differences in the daily weather during these and other, smaller fires, and in the two sets of fires’ responses to daily weather and antecedent atmospheric dryness. Twenty fires of unusual size (over 36 400 ha), were each paired with a nearby large fire (10 100 to 30 300 ha). Antecedent dryness and daily near-surface weather were compared for each set of fires. Growth response to daily weather was also examined for differences between the two sets of fires. Antecedent dryness measured as the Evaporative Demand Drought Index was greater for most of the fires of unusual size than it was for smaller fires. There were small differences in daily weather, with those differences indicating weather less conducive to fire growth for the unusually large fires than the smaller fires. Growth response was similar for the two sets of fires when weather properties were between 40th and 60th percentiles for each fire pair, but the unusually large fires’ growth was observably greater than the smaller fires’ growth for weather properties between the 80th to 100th percentiles. Response differences were greatest for wind speed, and for the Fosberg Fire Weather Index and variants of the Hot-Dry-Windy Index, which combine wind speed with atmospheric moisture.

The Hazards Posed by Mesoscale Lightning Megaflashes

Lighting megaflashes extending over >100 km distances have been observed by the Geostationary Lightning Mappers (GLMs) on NOAA’s 16-series Geostationary Operational Environmental Satellites (GOES). The hazards posed by megaflashes are unclear, however, due to limitations in the GLM data. We address these by reprocessing GOES-16 GLM measurements from 1/1/2018 to 1/15/2020 and integrating them with Earth Networks Global Lightning Network (ENGLN) observations. 194,880 GLM megaflashes are verified as natural lightning by ENGLN. Of these, 127,479 flashes occurred following the October 2018 GLM software update that standardized GLM timing. Reprocessed GLM/ENGLN lightning maps from these post-update cases provide a comprehensive view of how individual megaflashes evolve.This megaflash dataset is used to generate statistics that describe their hazards. The average megaflash produces 5-7 CG strokes that are spread across 40-50% of the flash extent. As flash extent increases beyond 100 km, megaflashes become concentrated in key hotspot regions in North and South America while the number of CG and IC events per flash and the overall peak current increase. CGs in the larger megaflashes occur over 80% of the flash extent measured by GLM, while the majority contain regions where the megaflash is the only lightning activity in the preceding hour. These statistics demonstrate that there is no safe location below an electrified cloud that is producing megaflashes and current lightning safety guidance is not always sufficient to mitigate megaflash hazards.

Variable impact of COVID-19 lockdown on air quality across 91 Indian cities

India responded to the COVID-19 pandemic through a three-phase nationwide lockdown: 25 March - 14 April, 15 April - 3 May and 4 - 17 May, 2020. We utilized this unique opportunity to assess the impact of restrictions on the air quality of Indian cities. We conducted comprehensive statistical assessments for the Air Quality Index (AQI) and criteria pollutant concentrations for 91 cities during the lockdown phases to the preceding seven days (pre-lockdown phase 18-24March,2020) and corresponding values from the same days of the year in 2019. Both comparisons show statistically significant country-wide mean decrease in AQI (33%), PM2.5 (36%), PM10 (40%), NO2 (58%), O3 (5%), SO2 (25%), NH3(28%), and CO(60%). These reductions represent a background or the lower bound of air quality burden of industrial and transportation sectors. The northern region was most impacted by the first two phases of the lockdown, while the southern region was most affectedin the last phase. The northeastern region was least affected, followed by the eastern region which also showed an increase in O3during the lockdown. Analysis of satellite retrieved Aerosol Optical Depth (AOD) shows that effects of restrictions on particulate pollution to be variable- locally confined in some areas or having a broader impact in other regions. Anomalous behavior over the eastern region suggestsa differing role of regional societal response or meteorology. The study results have policy implications as they provide the observational background values for the industrial and transportation sector’s contribution to urban pollution.

Conflict and Climate: Drivers of Fire Activity in Syria in the Twenty-First Century

It has been 10 years since the start of the Syrian uprisings. While relative stability is improving overall, a new disaster, wildfires, impacted an already food-insecure population by burning through key production areas, damaging crops, soil, and livestock and causing air quality to deteriorate. As observed with remotely sensed data, fire affected 4.8% of Syria in 2019, as compared with the average 0.2%, and most fires were observed within agricultural land in the northeast. Abnormal amounts of rainfall during the 2019 growing season and, consequently, high soil moisture explained about 62% of the drastic increase in the burned area extent. In contrast, in 2020, fires continued despite the average amount of rainfall. Extremely high temperature could partially explain a 10-fold increase in the extent of burned area in 2020 but only within forested regions in the northwest. We argue that the abrupt changes in Syria’s fire activity were driven by the complex interactions among conflict, migration, land use, and climate. On one side, the ongoing conflict leads to a drastic increase in the number of accidental and deliberate fires and reduced capacity for fire response. On the other side, years of insecurity, widespread displacement, and economic instability left no choice for locals other than exploiting fires to remove natural vegetation for expanding farming, logging, and charcoal trading. The loss of agricultural production and natural vegetation to fire can have serious implications for food security, soil property, biodiversity, and ecosystem services, which can further exacerbate the already unstable economy and make ongoing violence even more intense.

Snow-Pit Record from a Coastal Antarctic Site and Its Preservation of Meteorological Features

Polar snow pits or ice cores preserve valuable information derived from the atmosphere on past climate and environment changes. A 1.57-m snow-pit record from the coastal site (Styx Glacier) in eastern Antarctica covering the period from January 2011 to January 2015 was discussed and compared with meteorological variables. The dominant contribution of the deposition of sea-salt aerosols due to the proximity of the site to the ocean and processes of sea ice formation was revealed in the ionic concentrations. Consistent seasonal peaks in δ 18 O, δ D, MSA, , and indicate the strong enhancement of their source during warm periods, whereas the sea-salt ions (Na + , K + , Mg 2+ , Ca 2+ , Cl − , and ) exhibit a distinct distribution. Monthly mean δ 18 O positively correlates with the air temperature record from an automatic weather station (AWS) located in the main wind direction. Despite the shortness of the record, we suspect that the slight depletion of the isotopic composition and lowering of the snow accumulation could be related to the cooler air temperature with the decrease of open sea area. Consistency with previous studies and the positive correlation of sea-salt ions in the snow pit indicate the relatively good preservation of snow layers with noticeable climate and environmental signals [e.g., changes in sea ice extent (SIE) or sea surface temperature]. We report a new snow-pit record, which would be comparative and supportive to understand similar signals preserved in deeper ice cores in this location.

Drought Relief and Reversal over North America from 1500 to 2016

Season-to-season persistence of soil moisture drought varies across North America. Such interseasonal autocorrelation can have modest skill in forecasting future conditions several months in advance. Because robust instrumental observations of precipitation span less than 100 years, the temporal stability of the relationship between seasonal moisture anomalies is uncertain. The North American Seasonal Precipitation Atlas (NASPA) is a gridded network of separately reconstructed cool-season (December–April) and warm-season (May–July) precipitation series and offers new insights on the intra-annual changes in drought for up to 2000 years. Here, the NASPA precipitation reconstructions are rescaled to represent the long-term soil moisture balance during the cool season and 3-month-long atmospheric moisture during the warm season. These rescaled seasonal reconstructions are then used to quantify the frequency, magnitude, and spatial extent of cool-season drought that was relieved or reversed during the following summer months. The adjusted seasonal reconstructions reproduce the general patterns of large-scale drought amelioration and termination in the instrumental record during the twentieth century and are used to estimate relief and reversals for the most skillfully reconstructed past 500 years. Subcontinental-to-continental-scale reversals of cool-season drought in the following warm season have been rare, but the reconstructions display periods prior to the instrumental data of increased reversal probabilities for the mid-Atlantic region and the U.S. Southwest. Drought relief at the continental scale may arise in part from macroscale ocean–atmosphere processes, whereas the smaller-scale regional reversals may reflect land surface feedbacks and stochastic variability.

Variability in Isolated Convective Activity between Louisville, Kentucky, and Nearby Rural Locations

This study analyzes the frequency of strong, isolated convective cells in the vicinity of Louisville, Kentucky. Data from the Severe Weather Data Inventory are used to compare the frequency of convective activity over Louisville with the observed frequency at nearby rural locations from 2003 to 2019. The results show that Louisville experiences significantly more isolated convective activity than do the rural locations. The difference in convective activity between Louisville and the rural locations is strongest during summer, with peak differences occurring between May and August. Relative to the rural locations, Louisville experiences more isolated convective activity in the afternoon and early evening but less activity after midnight and into the early morning. Isolated convective events over Louisville are most likely during quiescent synoptic conditions, whereas rural events are more likely during active synoptic patterns. To determine whether these differences can be attributed primarily to urban effects, two additional cities are shown for comparison—Nashville, Tennessee, and Cincinnati, Ohio. Both Nashville and Cincinnati experience more isolated convective activity than all five of their nearby rural comparison areas, but the results for both are statistically significant at four of the five rural locations. In addition, the analysis of Cincinnati includes a sixth comparison site that overlaps the urbanized area of Columbus, Ohio. For that location, differences in convective activity are not statistically significant.