Changes In Atmospheric Moisture Research Articles

Heterogeneity in the Effects of Atmospheric Moisture Changes on Vegetation in Different Climatic Zones

Heterogeneity in the Effects of Atmospheric Moisture Changes on Vegetation in Different Climatic Zones

Response of Precipitation Increases to Changes in Atmospheric Moisture and Its Flux in the Columbia River Basin: WRF Model–Based Precipitation Maximization for PMP Studies

Response of Precipitation Increases to Changes in Atmospheric Moisture and Its Flux in the Columbia River Basin: WRF Model–Based Precipitation Maximization for PMP Studies

Emergent constraints on future extreme precipitation intensification: from global to continental scales

Extreme precipitation intensification due to global warming has received significant attention; however, large uncertainties remain regarding how much it will change in the future, even under a given greenhouse gas emissions pathway. Our constraining analysis provides smaller future extreme precipitation intensification with reduced uncertainties than raw/unconstrained model simulation projections from the global to continental scales and also several sub-continental areas. Historical warming trends in climate model simulations present strong positive inter-model correlations with future annual maximum daily precipitation intensification from the global to continental scales. This emergent relationship is employed for constraining analysis. The proposed emergent constraints are mostly associated with thermodynamics (atmospheric moisture changes), with limited contribution from dynamics (atmospheric circulation variations). This constraining framework has various advantages, including lower observation uncertainty, and more robust theoretical interpretation than previously suggested constraints for extreme precipitation frequency projections. CMIP6 models generally overestimate historically observed warming, which resultantly generates weaker extreme precipitation intensification following constraining analysis than unconstrained model simulation projections from the global to individual continents, and even several mid- and high-latitude sub-continental areas. Additionally, constrained projections exhibit narrower uncertainty ranges in future extreme precipitation projections. During the late 21st century (2070–2099), under the high-emission scenario (Shared Socioeconomic Pathway 5–8.5, characterized by fossil fueled development and a radiative forcing of 8.5 W m−2 in 2100), our results present reduced global average intensity and uncertainty for future annual maximum daily precipitation intensification by 25% and 27%, respectively.

Tracking Atmospheric Moisture Changes in Convective Storm Environments Using GEO ABI and LEO CrIS Data Fusion

The synergistic use of data from advanced space-borne instruments of different designs onboard different satellite platforms with different orbital tracks provides advantages in various applications over the use of individual data sets alone. For example, high vertical resolution sounding profiles from advanced sounders like CrIS (Cross-track Infrared Sounder) in a low Earth orbit (LEO) and a high horizontal plus temporal resolution radiance measurements from geostationary (GEO) imagers like ABI (Advanced Baseline Imager) can be effectively combined to benefit severe weather monitoring, prediction, and warning systems. The spatial and temporal fusion approach allows LEO products, such as atmospheric moisture, to be created with increased spatial detail at every GEO measurement time, generating a GEO hyperspectral sounder-like perspective. To demonstrate the potential benefit of a GEO and LEO (i.e., ABI and CrIS) data fusion to real-time applications, time sequences of the moisture profile fusion results are presented in two case studies, namely a tornado outbreak in Nebraska on 5 May 2021 and a severe storm occurrence in Texas on 24 May 2022. The implications of the fusion results for nowcasting and warning operations via comparisons to numerical model forecasts and weather radar reflectivity data are discussed.

Regime Changes in Atmospheric Moisture under Climate Change

Recent work attributing decadal regime changes in temperature to radiative forcing is extended to atmospheric moisture. Temperature, and specific and relative humidity (T, q, RH) from the HadISDH data set were analyzed for regime shifts using the bivariate test. Most shifts in q and T for global and northern hemisphere (NH), and tropical land occurred within a year of each other. Only one shift of q was recorded in the southern hemisphere (SH). RH increased in the NH in 1990–91 and decreased in a series of shifts from the late 1990s, while in the SH decreased from 2001. The tropics have remained neutral, shifting negative over land and positive over the ocean. The global decreases in 2001 and 2011 was −0.56%. Global RH from 32 climate models from the CMIP5 RCP4.5 archive all contained regime shifts but only 4 reached or exceeded the observed decreases by 2100, the earliest in 2056. Regime shifts in RH and fire danger over Australia are consistent with the SH decreases in RH, shifting within one year of global fire season length in 2002, showing that impacts are also being underestimated by current analyses. Methods for nonlinear attribution and the contributing processes for nonlinear change are discussed. These results show that developing a better understanding of nonlinear change in moisture-related climate risk is an urgent task.

Changes in the vegetation and water cycle of the Ecuadorian páramo during the last 5000 years

We analyzed changes in the long-term vegetation cover and in fire activity over the past 5000 years in the Ecuadorian páramo using a sediment core from Papallacta (Ecuador). The chronology is constrained by three tephra layers and 32 AMS 14C ages, and 168 samples yielded a high-resolution record of environmental changes. We estimated the upslope wind convectivity as the ratio between pollen transported from the Andean cloud forest and Poaceae pollen to distinguish changes in atmospheric moisture from changes in soil moisture. The record showed that the two sources of moisture, either from year-round adiabatic cloud dripping linked to SASM activity or to ENSO variability at decadal-scale, influenced vegetation-cover changes. Between 5000 and 2450 cal yr BP, both soil moisture and biomass burning were higher than after 2450 cal yr BP. The shift between the two states matches the zonal increase in summer insolation that drove the ITCZ to its southernmost position. Our results underline resilience to volcanic activity, the importance of the upslope convective dripping with the lowest convective index observed at ~4500 cal yr BP, the anomalous last century with the highest convective activity and the driest soil conditions recorded in the last 5000 years, the recent increase in fire activity and the link between soil moisture and the position of the ITCZ.

Large Divergence in Tropical Hydrological Projections Caused by Model Spread in Vegetation Responses to Elevated CO2

AbstractIncreasing atmospheric CO2 and associated global warming are expected to alter the global hydrological cycle, thereby posing widespread threats to freshwater availability. However, future hydrological projections differ greatly between models, particularly over the tropical regions. The large difference between model projections directly limits policy planning efforts, and the responsible modeling processes remain unclear. Here, we identify the primary processes accounting for model differences in tropical hydrological changes using multiple CO2 sensitivity experiments in the Coupled Model Intercomparison Project. We show that differences in projected changes to tropical evapotranspiration, precipitation, and surface water availability mainly arise from model representations of vegetation cover and stomatal conductance responses to elevated CO2 and associated changes in atmospheric moisture and circulation. Atmospheric responses to sea surface warming contribute additionally to the divergence in hydrological projections. Given the importance of vegetation responses to elevated CO2 and associated atmosphere feedbacks, our results underscore the need to improve representations of the vegetation physiological response to rising CO2 and its coupling to the atmosphere, to provide reliable tropical hydrological projections.

A 6000-year record of environmental change from Grand Cayman, British West Indies

Three sediment cores from North Sound lagoon provide a continuous record of environmental changes (atmospheric moisture and temperature) that have affected Grand Cayman, British West Indies, over the last ~6000 years. Changes in the facies and carbonate components indicate a transition from fresh-brackish-water coastal ponds to a fully marine environment, which coincided with global sea level rise ~2000 years ago. Variations in ∑REE + Y (4 to 45 ppm), Ti (6 to 71 ppm), and Fe (284 to 11,783 ppm) concentrations in these sediments reflect past changes in atmospheric moisture. Sea surface temperatures inferred from δ18O values of the sediments provide a record of past temperature fluctuations relative to the present-day average of 28 °C for North Sound. This includes two cool-dry periods (CD1 and CD2) from ~3850 to 1280 BCE and ~480 to 800 CE, two mild-wet periods (MW1 and MW2) from ~1280 to 200 BCE and ~1850 to 1980 CE, one warm-dry period (WD1) from ~200 BCE to 480 CE, and one cool-wet (CW1) period from ~800 to 1850 CE. These patterns are consistent with records from elsewhere in the Caribbean region. Accordingly, during MW1, CW1A, and MW2 the Intertropical Convergence Zone (ITCZ) was in a northern position and/or the North Atlantic Oscillation (NAO) was in a negative phase, resulting in increased atmospheric moisture and elevated temperatures. In contrast, CD1, WD1, and CD2, resulted from a southern position of the ITCZ and/or a positive phase of the NAO, resulting in low temperatures and decreased atmospheric moisture.

Effects of urban land expansion on decreasing atmospheric moisture in Guangdong, South China

It is known that rapid expansion in urban area exerts prominent effects on surface or near-surface temperature and the urban heat island effect. However, whether and how urban land expansion influences atmospheric humidity, a key indicator closely relating to human comfort and urban environment, warrant further investigations. By taking Guangdong Province as an example, in this study we examined the change in atmospheric moisture over South China during 1961–2014 and evaluated the urban expansion effects. We found a prominent drying tendency over Guangdong, as characterized by decreasing relative and specific humidities and increasing vapor pressure deficit. The drying trend has a positive correlation with urban expansion speed and exhibited regional differences, with particularly stronger trends in more urbanized and populated areas such as the Pearl River Delta. Using a dynamic classification of urban / rural stations based on time-varying high-resolution land use / land cover maps, we estimated that urbanization contributed to approximately 50% of the total drying trend in the urban areas of Guangdong. Possible mechanisms and processes underlying the urban expansion effect were also discussed. We suggested that the changes in atmospheric moisture and the urban expansion effect should be considered in future climate change mitigation, urban planning, and landscape design to support sustainable development in urban areas.

Spatial Patterns and Trends in Surface Air Temperatures and Implied Changes in Atmospheric Moisture Across the Hawaiian Islands, 1905–2017

AbstractWhile the Hawaiian Islands are experiencing long‐term warming, spatial and temporal patterns are poorly characterized. Drawing on daily temperature records from 309 stations (1905–2017), we explored relationships of surface air temperatures (Tmax, Tmin, Tavg, and diurnal temperature range) to atmospheric, oceanic, and land surface variables. Statistical modeling of spatial patterns (2006–2017) highlighted the strong negative influence of elevation and moisture on air temperature and the effects of distance inland, cloud frequency, wind speed, and the local trade wind inversion on the elevation dependence of surface air temperature. We developed time series of sea level air temperature and surface lapse rate by modeling surface air temperature as a simple function of elevation and found a strong long‐term (1905–2017) warming trend in sea level Tmin, twice that of Tmax (+0.17 vs +0.07°C/decade), suggesting regional warming, possibly enhanced by urbanization and cloud cover effects. Removing this trend, sea level Tmax and Tmin tracked SST and rainfall at decadal time scales, while Tmax increased with periods of weakened trade winds. Sea level air temperatures correlated with North Pacific climate indices, reflecting the influence of regional circulation via SST, rain, clouds, and trade winds that modulate environmental warming across the Hawaiian Islands. Increasing (steeper) Tmax surface lapse rates for the 0‐ to 1,600‐m elevation range (into the cloud zone) over 1978–2017 coincide with observations of marine boundary layer drying and rising cloud base heights, suggesting a need to better understand elevation‐dependent warming in this tropical/subtropical maritime environment and associated changes to cloud formation and persistence.

TRACKING THE ORIGIN OF MOISTURE OVER SERBIA USING THE LAGRANGIAN METHOD

In this study, we investigate the sources of moisture over Serbia using a Lagrangian method based on the FLEXPART V9.0 particle dispersion model combined with ERA-Interim reanalysis data, to track changes in atmospheric moisture. This approach computes the budget of evaporation-minus-precipitation by calculating changes in specific humidity along forward and backward trajectories. We considered a period of 34 years, from 1980 to 2014, which allowed the identification of climatological moisture sources and moisture transport towards the country. The results showed that Serbia receive moisture mainly from two sources: the Mediterranean Sea which is the dominant source during the winter (October-March) and the own region which predominate during the summer (April-September). Key words: moisture sources, Flexpart, Lagrangian method, Serbia

Multi‐scale observations of atmospheric moisture variability in relation to heavy precipitating systems in the northwestern Mediterranean during HyMeX IOP12

The deployment of special instrumentation for the Hydrological Cycle in the Mediterranean Experiment (HyMeX) provides a valuable opportunity to investigate the spatio‐temporal variability of atmospheric water vapour across scales in relationship with the occurrence of Heavy Precipitation Systems (HPSs) in the north Western Mediterranean (WMed) during the Intensive Observation Period (IOP12), which is the focus of this investigation. High‐resolution convection‐permitting COSMO simulations complement the observational network and allow the calculation of on‐line trajectories.In addition to the presence of a favourable large‐scale situation and low‐level convergence, atmospheric moisture changes resulting in conditionally unstable air are identified as responsible for convective initiation (CI). All HPSs within the north‐WMed form in periods/areas of maximum integrated water vapour (IWV; 35–45 kg/m2) after an increase of about 10–20 kg/m2. The most intense events receive moisture from different sources simultaneously and show a sudden increase of about 10 kg/m2 between 6 and 12 h prior to the event, whereas in the less intense events the increase is larger, about 20 kg/m2, over a period of at least 24–36 h. Changes in the lower (∼900 hPa) and mid‐troposphere (∼700 hPa) control the evolution of the atmospheric moisture and the instability increase prior to CI. Spatial inhomogeneities in the lower boundary layer determine the timing and location of deep convection, whereas enhanced moisture in the mid‐troposphere favours intensification. Moister and deeper boundary layers, with updraughts reaching up to 2 km are identified in those pre‐convective environments leading to HPS, whereas dry, shallow boundary layers are found everywhere else. The build‐up time and vertical distribution of the moisture changes are found to be crucial for the evolution and severity of the HPSs rather than the amount of total column atmospheric moisture.

Patterns of Evaporation and Precipitation Drive Global Isotopic Changes in Atmospheric Moisture

AbstractBecause water isotope ratios respond to phase changes during evaporation (E) and precipitation (P), they are candidate fingerprints of changing atmospheric hydrology. Moreover, through preservation in ice cores and other paleoproxies, they provide important insight into the past. Still, there is disagreement over what specific attributes of hydroclimate variability isotopes reveal. Here we argue that variations in zonal mean isotope ratios of water vapor and precipitation are largely a response to geographically shifting patterns of E and P. Differences in the relative importance of local versus remote changes in these moisture variables explain the apparent distinct isotopic sensitivities to temperature and precipitation amount in high and low latitudes, respectively. Not only does our work provide a unified framework for interpreting water isotopic measurements globally, but it also presents a novel approach for diagnosing water cycle changes in a warmer world.

Management Implications of Snowpack Sensitivity to Temperature and Atmospheric Moisture Changes in Yosemite National Park, CA

AbstractIn order to investigate snowpack sensitivity to temperature increases and end‐member atmospheric moisture conditions, we applied a well‐constrained energy‐ and mass‐balance snow model across the full elevation range of seasonal snowpack using forcing data from recent wet and dry years. Humidity scenarios examined were constant relative humidity (high) and constant vapor pressure between storms (low). With minimum calibration, model results captured the observed magnitude and timing of snowmelt. April 1 snow water equivalent (SWE) losses of 38%, 73%, and 90% with temperature increases of 2, 4, and 6°C in a dry year centered on areas of greatest SWE accumulation. Each 2°C increment of warming also resulted in seasonal snowline moving upslope by 300 m. The zone of maximum melt was compressed upward 100–500 m with 6°C warming, with the range reflecting differences in basin hypsometry. Melt contribution by elevations below 2,000 m disappeared with 4°C warming. The constant‐relative‐humidity scenario resulted in 0–100 mm less snowpack in late spring vs. the constant‐vapor‐pressure scenario in a wet year, a difference driven by increased thermal radiation (+1.2 W/m2) and turbulent energy fluxes (+1.2 W/m2) to the snowpack for the constant‐relative‐humidity case. Loss of snowpack storage and potential increases in forest evapotranspiration due to warming will result in a substantial shift in forest water balance and present major challenges to land management in this mountainous region.

Vegetation responses to late Holocene climate changes in an Andean forest

AbstractA paleoecological record from Lake Palotoa (1370 m elevation) in the Andean foothills of Peru spans the last 3800 years. Lake Palotoa lies near the modern cloud base in a location sensitive to changes in atmospheric moisture. In many areas, these forests have been destroyed, but Lake Palotoa shows no sign of human occupation today or in the past. The modern forest surrounding the lake is dominated by the Andean palm, Dictyocaryum lamarckianum, which is also the most abundant taxon in the fossil pollen record. Fossil pollen data show the vegetation assemblages have not experienced strong compositional changes in the late Holocene. Global-scale climatic events such as the Medieval Climate Anomaly (MCA) and the Little Ice Age (LIA) are identified within the record, though the vegetation responses are subtle. Hedyosmum and Sloanea pollen percentages increase near the onset of the MCA and may reflect decreased seasonality. The LIA coincides with increased Hedyosmum pollen percentages, and increases in Clethra and Begonia, two elements that tend to occupy forests now found at higher elevations. Our findings demonstrate the stability of montane forest systems to natural Holocene climate change.

Shifts in historical streamflow extremes in the Colorado River Basin

The global phenomenon of climate change-induced shifts in precipitation leading to “wet regions getting wetter” and “dry regions getting drier” has been widely studied. However, the propagation of these changes in atmospheric moisture within stream channels is not a direct relationship due to differences in the timing of how changing precipitation patterns interact with various land surfaces. Streamflow is of particular interest in the Colorado River Basin (CRB) due to the region’s rapidly growing population, projected temperature increases that are expected to be higher than elsewhere in the contiguous United States, and subsequent climate-driven disturbances including drought, vegetation mortality, and wildfire, which makes the region more vulnerable to changes in hydrologic extremes. Here, we determine how streamflow extremes have shifted in the CRB using two statistical methods—the Mann-Kendall trend detection analysis and Generalized Extreme Value (GEV) theorem. We evaluate these changes in the context of key flow metrics that include high and low flow percentiles, maximum and minimum 7-day flows, and the center timing of streamflow using historical gage records representative of natural flows. Monthly results indicate declines of up to 41% for high and low flows during the June to July peak runoff season, while increases of up to 24% were observed earlier from March to April. Our results highlight a key threshold elevation and latitude of 2300m and 39° North, respectively, where there is a distinct shift in the trend. The spatiotemporal patterns observed are indicative of changing snowmelt patterns as a primary cause of the shifts. Identification of how this change varies spatially has consequences for improved land management strategies, as specific regions most vulnerable to threats can be prioritized for mitigation or adaptation as the climate warms.

Tracking the Origin of Moisture over the Danube River Basin Using a Lagrangian Approach

In this study, we investigate the sources of moisture (and moisture for precipitation) over the Danube River Basin (DRB) by means of a Lagrangian approach using the FLEXPART V9.0 particle dispersion model together with ERA-Interim reanalysis data to track changes in atmospheric moisture over 10-day trajectories. This approach computes the budget of evaporation-minus-precipitation by calculating changes in specific humidity along forward and backward trajectories. We considered a time period of 34 years, from 1980 to 2014, which allowed for the identification of climatological sources and moisture transport towards the basin. Results show that the DRB mainly receives moisture from seven different oceanic, maritime, and terrestrial moisture source regions: North Atlantic Ocean, North Africa, the Mediterranean Sea, Black Sea, Caspian Sea, the Danube River Basin, and Central and Eastern Europe. The contribution of these sources varies by season. During winter (October–March) the main moisture source for the DRB is the Mediterranean Sea, while during summer (April–September) the dominant source of moisture is the DRB itself. Moisture from each source has a different contribution to precipitation in the DRB. Among the sources studied, results show that the moisture from the Mediterranean Sea provides the greatest contribution to precipitation in the basin in both seasons, extending to the whole basin for the winter, but being more confined to the western side during the summer. Moisture from the Caspian and Black Seas contributes to precipitation rather less.

Observed near-surface atmospheric moisture content changes affected by irrigation development in Xinjiang, Northwest China

The effects of irrigation development on observed near-surface atmospheric moisture changes remain unclear in arid Xinjiang. In this study, cultivated land fractions (CFs) within a 4-km radius of 90 meteorological stations over Xinjiang, which are inferred from the 2000 land use map, are used as a quantitative indicator of irrigation intensity. Trends of observed water vapor pressure and relative humidity during the growing season (May to September) from 1959 to 2006 are significantly positively correlated with CFs of the meteorological stations. Stations with larger CFs experience a more rapid increase in near-surface atmospheric moisture than stations with small CFs. Results indicate that growing season near-surface atmospheric moisture wetting is enhanced by irrigation development for stations with high levels of cultivated land uses. The land use around stations should be considered when analyzing the observed near-surface atmospheric moisture changes in Xinjiang.

Climatic controls and climate proxy potential of Lewis Glacier, Mt. Kenya

Abstract. The Lewis Glacier on Mt. Kenya is one of the best studied tropical glaciers and has experienced considerable retreat since a maximum extent in the late 19th century (L19). From distributed mass and energy balance modelling, this study evaluates the current sensitivity of the surface mass and energy balance to climatic drivers, explores climate conditions under which the L19 maximum extent might have been sustained, and discusses the potential for using the glacier retreat to quantify climate change. Multi-year meteorological measurements at 4828 m provide data for input, optimization, and evaluation of a spatially distributed glacier mass balance model to quantify the exchanges of energy and mass at the glacier–atmosphere interface. Currently the glacier loses mass due to the imbalance between insufficient accumulation and enhanced melt, because radiative energy gains cannot be compensated by turbulent energy sinks. Exchanging model input data with synthetic climate scenarios, which were sampled from the meteorological measurements and account for coupled climatic variable perturbations, reveals that the current mass balance is most sensitive to changes in atmospheric moisture (via its impact on solid precipitation, cloudiness, and surface albedo). Positive mass balances result from scenarios with an increase of annual (seasonal) accumulation of 30 % (100 %), compared to values observed today, without significant changes in air temperature required. Scenarios with lower air temperatures are drier and associated with lower accumulation and increased net radiation due to reduced cloudiness and albedo. If the scenarios currently producing positive mass balances are applied to the L19 extent, negative mass balances are the result, meaning that the conditions required to sustain the glacier in its L19 extent are not reflected in today's meteorological observations using model parameters optimized for the present-day glacier. Alternatively, a balanced mass budget for the L19 extent can be achieved by changing both climate and optimized gradients (used to extrapolate the meteorological measurements over the glacier) in a manner that implies a distinctly different coupling between the glacier's local surface-air layer and its surrounding boundary layer. This result underlines the difficulty of deriving palaeoclimates for larger glacier extents on the basis of modern measurements of small glaciers.

Changes of summer precipitation in China: The dominance of frequency and intensity and linkage with changes in moisture and air temperature

AbstractUsing observed precipitation and the National Centers for Environmental Prediction–National Center for Atmospheric Research reanalysis, the changes in the metrics of the summer precipitation in China, the dominance of frequency and intensity of daily extreme precipitation, and the linkage with changes in moisture and air temperature are explored. Results show that over the recent 50 years, the total summer rainfall increased over the southeast and the west and decreased over the northeast. The changes in the frequency, identified with the 95% threshold and Poisson regression, and rainfall extremes show similar spatial patterns. The relative importance of the changes in frequency and intensity in the variability and changes in extreme precipitation are estimated. It is shown that, while the interannual variability of the rainfall amount is dominated by the frequency change in almost all stations, the long‐term change of rainfall amount can be dominated by both frequency and intensity, depending on the station. The change in the rainfall total is linked to changes in atmospheric moisture and temperature. The results show that the variability and change of the rainfall total can be dominated by changes in both moisture and air temperature, and the relative importance depends on the region.