Changes in the Duration of the Navigation Period in Arctic Seas along the Northern Sea Route in the Twenty-First Century: Bayesian Estimates Based on Calculations with the Ensemble of Climate Models

Doklady Earth Sciences - The duration of the navigation period (DNP) on the Northern Sea Route (NSR) and in some parts of it in the twenty-first century has been analyzed based on the models of the...     

Cryogenically cooled low-noise amplifier for radio-astronomical observations and centimeter-wave deep-space communications systems

We report a design solution for a highly reliable, low-noise and extremely efficient cryogenically cooled transmit/receive unit for a large antenna system meant for radio-astronomical observations and deep-space communications in the X band. We describe our design solution and the results of a series of laboratory and antenna tests carried out in order to investigate the properties of the cryogenically cooled low-noise amplifier developed. The transmit/receive unit designed for deep-space communications (Mars missions, radio observatories located at Lagrangian point L2, etc.) was used in practice for communication with live satellites including “Radioastron” observatory, which moves in a highly elliptical orbit.     

Model Estimates of Global and Regional Climate Changes in the Holocene

Doklady Earth Sciences - On the basis of simulations using a global climate model, the global and regional climate changes in the Holocene are estimated. According to our results, the average...     

Impact of Sulfur Dioxide on the Terrestrial Carbon Cycle

Izvestiya, Atmospheric and Oceanic Physics - This paper updates the results obtained earlier with the climate model developed at the A.M. Obukhov Institute of Atmospheric Physics of the Russian...     

Simulation of thermal and hydrological regimes of Siberian river watersheds under permafrost conditions from reanalysis data

A one-dimensional dynamic model of heat and moisture transfer in the soil has been developed. The use of the ERA-40 reanalysis as input data makes it possible to compute characteristics of the soil thermal and hydrological regimes, including watershed runoff, from specified climatic characteristics of the atmosphere. Results are presented of numerical experiments on a comparison of the model estimates of the depths of seasonal thawing with observations at several Siberian stations. For the latter half of the 20th century, the depths of seasonal thawing are mapped and runoff from watersheds of the largest Siberian rivers is computed. The model reproduces observed runoff variations. For the Ob basin, the model-derived runoff estimates agree well with observational data if peat deposits in the upper 2-m layer are taken into account.     

Comparison of climatic efficiency of the mechanisms of land-surface albedo changes caused by land use

Changes in ecosystem types, including situations when natural vegetation is replaced by agricultural lands, leads to surface albedo changes and the development of the corresponding short-wave radiative forcing (RF). This work analyzes ensemble numerical experiments with the climatic model (CM) of the Institute of Atmospheric Physics at the Russian Academy of Sciences (IAP RAS) for the 16th–21st centuries. The responses to changes in the contents of greenhouse gases and sulfate aerosols (tropospheric and stratospheric), in the solar constant, and in the land-surface albedo when natural vegetation is replaced by agricultural lands were modeled during these experiments. Different members of these ensemble experiments were obtained by varying the model parameters affecting the RF on the climate during land use: the albedo of agricultural lands was varied within the interval from 0.15 to 0.25 and the parameter controlling the efficiency of snow masking by tree vegetation was varied in the range from the absence of this effect to its maximally possible efficiency. It has been established that changes in surface albedo when natural vegetation is replaced by agricultural lands have the largest influence on the globally averaged annual mean RF at the top of the atmosphere, whereas the influence of snow masking on the RF is substantially less. This phenomenon is caused by the fact that snow masking by tree vegetation can take place only in winter in regions of temperate and high latitudes, when insolation is relatively low. A comparison of the spatial structure of the annual mean response of the surface temperature with the HadCRUT3v and GISS observational data makes it possible to narrow the admissible range of model parameter values. In particular, it can be inferred that the key parameter values which control the influence that land use has on the surface albedo in the IAP RAS CM are close to optimal. In addition, variations in these parameters do not lead to a significant influence of land use on climate change in the 21st century if the Land Use Harmonization (LUH) scenarios of changes in the area of agricultural lands are used: the uncertainty of the model response associated with the uncertainty of values of such controlling parameters in the 21st century does not exceed 0.1 K.     

Influence of direct sulfate-aerosol radiative forcing on the results of numerical experiments with a climate model of intermediate complexity

The climate model of intermediate complexity developed at the Institute of Atmospheric Physics of the Russian Academy of Sciences (IAP RAS CM) is extended by a block for the direct anthropogenic sulfate-aerosol (SA) radiative forcing. Numerical experiments have been performed with prescribed scenarios of the greenhouse and anthropogenic sulfate radiative forcings from observational estimates for the 19th and 20th centuries and from SRES scenarios A1B, A2, and B1 for the 21st century. The globally averaged direct anthropogenic SA radiative forcing F _ASA by the end of the 20th century relative to the preindustrial state is ?0.34 W/m², lying within the uncertainty range of the corresponding present-day estimates. The absolute value of F _ASA is the largest in Europe, North America, and southeastern Asia. A general increase in direct radiative forcing in the numerical experiments that have been performed continues until the mid-21st century. With both the greenhouse and the sulfate loadings included, the global climate warming in the model is 1.5–2.8 K by the end of the 21st century relative to the late 20th century, depending on the scenario, and 2.1–3.4 K relative to the preindustrial period. The sulfate aerosol reduces global warming by 0.1–0.4 K in different periods depending on the scenario. The largest slowdown (>1.5 K) occurs over land at middle and high latitudes in the Northern Hemisphere in the mid-21st century for scenario A2. The IAP RAS CM response to the greenhouse and the aerosol forcing is not additive.