Abstract. Precipitation measurements exhibit large coldseason biases due to under-catch in windy conditions. These uncertainties affect water balance calculations, snowpack monitoring and calibration of remote sensing algorithms and land surface models. More accurate data would improve the ability to predict future changes in water resources and mountain hazards in snow-dominated regions.In 2010, a comprehensive test site for precipitation measurements was established on a mountain plateau in southern Norway. Automatic precipitation gauge data are compared with data from a precipitation gauge in a Double Fence Intercomparison Reference (DFIR) wind shield construction which serves as the reference. A large number of other sensors are provided supporting data for relevant meteorological parameters.In this paper, data from three winters are used to study and determine the wind-induced under-catch of solid precipitation. Qualitative analyses and Bayesian statistics are used to evaluate and objectively choose the model that best describes the data. A continuous adjustment function and its uncertainty are derived for measurements of all types of winter precipitation (from rain to dry snow). A regression analysis does not reveal any significant misspecifications for the adjustment function, but shows that the chosen model does not describe the regression noise optimally. The adjustment function is operationally usable because it is based only on data available at standard automatic weather stations.The results show a non-linear relationship between undercatch and wind speed during winter precipitation events and there is a clear temperature dependency, mainly reflecting the precipitation type. The results allow, for the first time, derivation of an adjustment function based on measurements above 7 m s −1 . This extended validity of the adjustment function shows a stabilization of the wind-induced precipitation loss for higher wind speeds.
Abstract. The impact of future emissions from aviation and shipping on the atmospheric chemical composition has been estimated using an ensemble of six different atmospheric chemistry models. This study considers an optimistic emission scenario (B1) taking into account e.g. rapid introduction of clean and resource-efficient technologies, and a mitigation option for the aircraft sector (B1 ACARE), assuming further technological improvements. Results from sensitivity simulations, where emissions from each of the transport sectors were reduced by 5 %, show that emissions from both aircraft and shipping will have a larger impact on atmospheric ozone and OH in near future (2025; B1) and for longer time horizons (2050; B1) compared to recent time (2000). However, the ozone and OH impact from aircraft can be reduced substantially in 2050 if the technological improvements considered in the B1 ACARE will be achieved.Shipping emissions have the largest impact in the marine boundary layer and their ozone contribution may exceed 4 ppbv (when scaling the response of the 5 % emission perturbation to 100 % by applying a factor 20) overCorrespondence to: Ø. Hodnebrog (oivind.hodnebrog@geo.uio.no) the North Atlantic Ocean in the future (2050; B1) during northern summer (July). In the zonal mean, shipinduced ozone relative to the background levels may exceed 12 % near the surface. Corresponding numbers for OH are 6.0 × 10 5 molecules cm −3 and 30 %, respectively. This large impact on OH from shipping leads to a relative methane lifetime reduction of 3.92 (±0.48) % on the global average in 2050 B1 (ensemble mean CH 4 lifetime is 8.0 (±1.0) yr), compared to 3.68 (±0.47) % in 2000.Aircraft emissions have about 4 times higher ozone enhancement efficiency (ozone molecules enhanced relative to NO x molecules emitted) than shipping emissions, and the maximum impact is found in the UTLS region. Zonal mean aircraft-induced ozone could reach up to 5 ppbv at northern mid-and high latitudes during future summer (July 2050; B1), while the relative impact peaks during northern winter (January) with a contribution of 4.2 %. Although the aviation-induced impact on OH is lower than for shipping, it still causes a reduction in the relative methane lifetime of 1.68 (±0.38) % in 2050 B1. However, for B1 ACARE the perturbation is reduced to 1.17 (±0.28) %, which is lower than the year 2000 estimate of 1.30 (±0.30) %.Based on the fully scaled perturbations we calculate net radiative forcings from the six models taking into account Published by Copernicus Publications on behalf of the European Geosciences Union. 11294 Ø. Hodnebrog et al.: Impact of scenario B1 traffic emissions on ozone and OH ozone, methane (including stratospheric water vapour), and methane-induced ozone changes. For the B1 scenario, shipping leads to a net cooling with radiative forcings of −28.0 (±5.1) and −30.8 (±4.8) mW m −2 in 2025 and 2050, respectively, due to the large impact on OH and, thereby, methane lifetime reductions. Corresponding values for the aviation sector shows a...
Abstract. Precipitation measurements exhibit large cold-season biases due to under-catch in windy conditions. These uncertainties affect water balance calculations, snowpack monitoring and calibrations of remote sensing algorithms and land surface models. More accurate data would improve the ability to predict future changes in water resources and mountain hazards in snow-dominated regions. In 2010, an extensive test-site for precipitation measurements was established at a mountain plateau in Southern Norway. Precipitation data of automatic gauges were compared with a precipitation gauge in a Double Fence Intercomparison Reference (DFIR) wind shield construction which served as the reference. Additionally, a large number of sensors were monitoring supportive meteorological parameters. In this paper, data from three winters were used to study and determine the wind-induced under-catch of solid precipitation. Qualitative analyses and Bayesian statistics were used to evaluate and objectively choose the model that is describing the data best. A continuous adjustment function and its uncertainty were derived for measurements of all types of winter precipitation (from rain to dry snow). A regression analysis did not reveal any significant misspecifications for the adjustment function, but showed that the chosen model uncertainty is slightly insufficient and can be further optimized. The adjustment function is operationally usable based only on data available at standard automatic weather stations. Our results show a non-linear relationship between under-catch and wind speed during winter precipitation events and there is a clear temperature dependency, mainly reflecting the precipitation type. The results allowed for the first time to derive an adjustment function with a data-tested validity beyond 7 m s−1 and proved a stabilisation of the wind-induced precipitation loss for higher wind speeds.
Abstract. Emissions of short-lived climate forcers (SLCF) in the Arctic region are expected to increase, notably from shipping and petroleum extraction. We here discuss changes in atmospheric SLCF concentrations and resulting radiative forcing (RF) from present day shipping and petroleum activities in the Arctic. The three-dimensional chemistry transport OsloCTM2 and a state of the art radiative forcing model are used, based on a coherent dataset of present day Arctic emissions. We find that the net RF of SLCF of shipping in the Arctic region is negative, mainly due to the direct and indirect RF effects of sulphate emissions, while the net RF of SLCF of petroleum extraction is positive, mainly due to the effects of black carbon aerosols in the air and deposited on snow. Strong seasonal variations of the sensitivities to emissions are found. In terms of annual mean values we find that the Arctic sensitivities to SLCF is similar to global average sensitivities. One exception to this is the stronger snow/ice albedo effect from BC emissions.
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