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In this study we investigate the effect of different downscaling methods on the hydrologic cycle of a Mediterranean catchment in Sardinia (Italy) that is prone to extreme flooding. To this aim, we use an ensemble of four combinations of GCM - RCM projections (see Deidda et al., 2013, and Langousis et al., 2016), statistically downscaled using: a) the parametric statistical scheme of Mamalakis et al. (2017), and b) its widely used non-parametric variant based on empirically derived Q-Q (quantile-quantile) correction relationships. In particular, we analyze differences in the climate projections of the available downscaled climate model outputs, considering or not the elevation factor (in the latter case by re-projecting outputs at the mean elevation of the basin). We further quantify the impact of these differences on modeled hydrologic variables. The hydrologic impact of climate change is evaluated during five 30-year periods (1951-1980, 1981-2010, 2011-2040, 2041-2070, 2071-2100), focusing on a set of variables that characterize the water balance, including precipitation, air temperature, discharge, leakage, and actual evapotranspiration. The response of the basin is quantified at the outlet and also at 33 subcatchments, analyzing the influence of features such as the area and mean elevation of the subcatchments. The results show that the choice of climate model and downscaling method leads to variations in the simulated hydrologic response of the basin, and that this effect varies also by subwatershed. Notwithstanding these differences, the reduction in precipitation predicted by the climate models is more pronounced as the watershed area increases, and as the altitude decreases. References:Deidda, R., M. Marrocu, G. Caroletti, G. Pusceddu, A. Langousis, V. Lucarini, M. Puliga, and A. Speranza (2013). Regional climate models' performance in representing precipitation and temperature over selected Mediterranean areas, Hydrol. Earth Syst. Sci., 17(12), 5041-5059, doi:10.5194/hess-17-5041-2013.Langousis, A., A. Mamalakis, R. Deidda and M. Marrocu (2016). Assessing the relative effectiveness of statistical downscaling and distribution mapping in reproducing rainfall statistics based on climate model results, Water Resour. Res., 52, doi:10.1002/2015WR017556.Mamalakis, A., A. Langousis, R. Deidda, and M. Marrocu (2017). A parametric approach for simultaneous bias correction and high-resolution downscaling of climate model rainfall, Water Resour. Res., 53, doi:10.1002/2016WR019578. [ABSTRACT FROM AUTHOR]

Assessment of the impacts of climate change on hydrological regime is important for sustainable water resources management. The objective of this study is to assess the impacts of future climate changes on the hydrological regime of the headwater catchment of the Vistucky Creek (area 9.8 km2) in south-western Slovakia. Changes in climatic characteristics (i.e., precipitation and air temperature) for periods 2022-2060 and 2062-2100 were prepared by two regional climate models KNMI and MPI using the A1B emission scenario (average related to fossil carbon production). Both climatic scenarios assume increase in the air temperature and precipitation (higher in winter than in summer). A lumped conceptual rainfall-runoff model (the HBV-based TUW model) was used to simulate the catchment hydrological behaviour. The TUW model was calibrated for the reference period of 1982 – 2008. The calibration of the model was performed 50 times with a differential evolution algorithm. After obtaining the collection of the 50 parameter sets, the best set (in terms of Nash-Sutcliffe efficiency and the volume error) was chosen. This set of model parameters was used for the simulation of long-term mean monthly runoff for the three periods (i.e., 1982-2008, 2022-2060, and 2062-2100).The results show that changes in the long-term runoff seasonality and extremality of hydrological cycle could be expected in the future if the climate changes as the scenarios assume. The runoff should increase in autumn and winter months (i.e., from September to February) and decrease in spring and summer months (i.e, from April to August) compared to the reference period. Peakflows should increase in period 2062-2100 while discharge minima should slightly decrease (only for the climatic data from the KNMI model). It indicates possible increase in flow extremality. Catchment water storage as expressed by the soil moisture index and baseflow should decrease in period 2062-2100, especially according to climatic data from the KNMI model. Our contribution will discuss these changes in hydrological regime in the climate change context.AcknowledgmentThis work was supported by the Slovak Research and Development Agency under the contract No. APVV-15-0497. [ABSTRACT FROM AUTHOR]

The unabated shrinkage of Himalayan glaciers contributes to sea level rise and affects the regional water cycle. Many glacier monitoring studies have employed modelling or remote sensing approaches, whereas there have been comparatively few in situ observational studies owing to the difficulties in accessing these high-altitude glaciers. Furthermore, in situ observations are generally limited to lower elevations, with the observed mass balances being significantly more negative than remote sensing estimates of regional-scale glacier mass balance. We therefore conducted a mass-balance study of debris-free Trambau Glacier in the Rolwaling region, Nepal Himalaya, which is accessible to 6000 m a.s.l., to better understand mass-balance processes and the effect of precipitation on these processes on high-elevation Himalayan glaciers. Continuous in situ meteorological and mass-balance observations that spanned the two melt seasons since May 2016 are presented. An energy- and mass-balance model is also applied to evaluate its performance and sensitivity to various climatic conditions. The 2016 melt season (2016) and 2016/17 year-long mass-balance observations are both negative. Estimated glacier-wide mass balances of −0.40 and −0.75 m w.e. in 2016 and 2016/17, respectively, are obtained by combining the observed and modelled mass balances below/above the highest stake at 5850 m a.s.l. The estimated long-term glacier mass balance, which is reconstructed using the ERA-Interim data calibrated with the in situ data, is −0.76 ± 0.41 m w.e. a−1 for the period 1980–2017. A significant correlation with annual precipitation (r = 0.76, p < 0.001) is observed, whereas there is no discernible correlation with mean summer air temperature. The results indicate the continuous mass loss of Trambau Glacier over the last four decades, which contrasts with the steady state of neighbouring Mera Glacier. [ABSTRACT FROM AUTHOR]

The Arctic water cycle is undergoing pronounced change in the atmosphere, hydrosphere, and cryosphere. Reduced albedo due to declining sea ice extent is amplifying Arctic temperatures and atmospheric humidity, leading to complex seasonal patterns of synoptic climate, evaporation and precipitation. To better understand, quantify, and monitor these changes, in December 2017 we installed a new Picarro continuous water vapor analyzer at the Finnish Meteorological Institute's research station in Pallas-Yllästunturi National Park, 170 km north of the Arctic Circle. Here, we pair real-time (1 second) water vapor isotope measurements (δ18O, δ2H) with a suite of meteorological parameters − including air temperature, relative humidity, solar flux, wind speed and direction – as well as a Lagrangian moisture source diagnostic for isotopic fingerprinting of atmospheric transport pathways. Pallas vapor compositions range between -20 to -38 ‰ for δ18O and -140 to -300 ‰ for δ2H, and exhibit pronounced diurnal, weekly, monthly and seasonal fluctuations. We use the deuterium excess parameter (d-excess; δ2H−8.δ18O) to partition the water vapor flux from different moisture source regions across the Arctic and sub-Arctic. Of note is the observation that d-excess values oscillate substantially (> ±20 ‰) and rapidly in response to shifting synoptic conditions and divergent storm tracks; for example, switching from vapor derived in the eastern Barents and Kara Seas to vapor from the North Atlantic or Greenland Sea, and these nuances are further explored in relation to sea ice coverage or lack thereof. Delineating these changes at such fine definition using our land-based system are key to reconciling how a changing Arctic system with reduced sea ice and divergent ocean temperatures are altering typical patterns of synoptic weather, for example the remarkable winter and spring snow conditions that blanketed much of northern Europe and North America in 2018. [ABSTRACT FROM AUTHOR]

Mars Science laboratory (MSL) has been operating successfully since early August 2012 with the REMS instrument providing extremely valuable atmospheric observations of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements.The REMS-H relative humidity device is based on polymeric capacitive humidity sensors developed by Vaisala Inc. and it makes use of three (3) humidity sensor heads. The humidity device is mounted on the REMS boom providing ventilation with the ambient atmosphere through a filter protecting the device from airborne dust. The REMS-H humidity instrument has created an unprecedented data record of more than two full Martian years.It has measured the relative humidity and temperature at 1.6 m height for a period of 5 minutes every hour as part of the MSL/REMS instrument package. Mars Science laboratory (MSL) has been operating successfully since early August 2012 with the REMS instrument providing extremely valuable atmospheric observations of atmospheric pressure, temperature of the air, ground temperature, wind speed and direction, relative humidity (REMS-H), and UV measurements.The annual in situ water cycle based on three full Martian years at the Gale crater will be discussed. We will utilize the REMS-H instrument's in situ observations accompanied by orbital observations and modeling efforts. We will infer the hourly atmospheric VMR from the REMS-H observations and compare these VMR measurements with predictions of VMR given by our 1D column Martian atmospheric/regolith model to investigate the local water cycle, exchange processes and the local climate in Gale Crater.The strong diurnal variation suggests there are surface-atmosphere exchange processes at Gale Crater during all seasons, which deplete moisture to the ground in the evening and nighttime and release the moisture back to the atmosphere during the daytime. Our modeling results presumably indicate that adsorption processes take place during the nighttime and desorption during the daytime. Other processes, e.g. convective turbulence play a significant role in the daytime in conveying the moisture into the atmosphere. A clear increase in the amount of early morning atmospheric humidity was detected from about sol 1800 onward, when Curiosity started to climb onto Mt. Sharp. The MSL MastCam pictures from this time show exposed bedrock scenery with very sparse and thin layers of wind-blown dust. Our simulations indicate that a plausible explanation for the increase of the atmospheric humidity during early mornings could be the Mt Sharp bedrock material a higher inertia low porosity of an exposed bedrock material. [ABSTRACT FROM AUTHOR]