No treeline shift despite climate change over the last 70 years

Background:The recent rise in temperature and shifting precipitation regimes threaten ecosystems around the globe to different degrees.Treelines are expected to respond to climate warming by shifting to higher elevations,but it is unclear whether they can track temperature changes.Here,we integrated high-resolution aerial imagery with local climatic and topographic characteristics to study the treeline dynamic from 1945 to 2015 on the semiarid Mediterranean island of Crete,Greece.Results:During the study period,the mean annual temperature at the treeline increased by 0.81℃,while the average precipitation decreased by 170 mm.The treeline is characterized by a diffuse form,with trees growing on steep limestone slopes(>50°)and shallow soils.Moreover,the treeline elevation decreases with increasing distance from the coast and with aspect(south>north).Yet,we found no shift in the treeline over the past 70 years,despite an increase in temperature in all four study sites.However,the treeline elevation correlated strongly with topographic exposure to wind(R^(2)=0.74,p<0.001).Therefore,the temporal lag in treeline response to warming could be explained by a combination of topographic and microclimatic factors,such as the absence of a shelter effect and a decrease in moisture.Conclusion:Although there was no treeline shift over the last 70 years,climate change has already started shifting the treeline altitudinal optimum.Consequently,the lack of climate-mediated migration at the treeline should raise concerns about the threats posed by warming,such as drought damages,and wildfire,especially in the Mediterranean region.Therefore,conservation management should discuss options and needs to support adaptive management.

Development of Broadband LHCP Pyramidal Horn Antenna with Septum Gaussian Profile Polarizer for CP-SAR Sensor Onboard Microsatellite

Horn Antenna has many applications such as communication, radar, and standard reference antenna for measurement. In this research, we designed a pyramidal horn for a Circularly Polarized Synthetic Aperture Radar (CP-SAR) sensor onboard a microsatellite. We utilized a 3D printer with Fused Deposition Modelling (FDM) technology for fast, low-cost, and low-weight production. Polylactide (PLA) material was used to construct 3D structures, and a copper conductive coating was painted on its surface. Gaussian distribution function was employed to create a septum polarizer profile. NPC-220 A with 1.6 thickness and 2.17 dielectric constant was used to make a microstrip monopole antenna and stripline feeding to feed the pyramidal horn to generate TE01 mode at one side of the waveguide. The design, parametric studies, and measurements are discussed in this paper. The designed antenna can achieve wide bandwidth 28% of 3 dB axial ratio, and more than 22% of s11 ≤ &minus;10 dB in working frequency that is acceptable for CP-SAR requirement on the microsatellite.

The Application of FDTD and Micro Genetic Algorithms on the Planar Spiral Inductors

High Q inductors are the important elements for RF circuit design. In this paper, the FDTD method is applied to explain the crowding effect of the spiral inductor , which can never be accurately analyzed by analytical solutions. The experimental results verify the FDTD simulation. The micro genetic algorithms and FDTD are combined to design the high Q of the inductor, the results show the efficiency of this exploration.

Calibration and brightness temperature algorithm of CE-1 Lunar Microwave Sounder (CELMS)

CE-1 Lunar Microwave Sounder (CELMS) is the first passive microwave radiometer in the world to sound the surface of the Moon in the lunar orbit at altitude of 200 km. The scientific objective of CELMS is to obtain global brightness temperature (TB) of the Moon, to retrieve information on lunar regolith, and to evaluate the distribution of helium-3 on the Moon implanted by solar wind. Before launch of CELMS, a series of experiments were carried out in laboratories to test the performances of the systems, and to calibrate the responses between the input of TB and the output of voltage from the receivers. However, the thermal condition exposed to CELMS is more complicated in lunar orbit than on the Earth, which makes the temperatures of different parts of CELMS wave vary greatly, and the cosmic background is not very clean due to the pointing of cold space antenna to the direction of the satellite running, which brings uncertainties into data-processing of CELMS when the temperature of cold space is used as a calibrator. Furthermore, the lack of knowledge on the lunar ingredients and compositions, distributions of physical temperatures, and properties on lunar microwave radiation leads to difficulties in validating the measurements and retrievals of CELMS. By analyzing the results of ground experiments and the measurements of CELMS in-orbit, along with our knowledge of the properties of lunar surface, here we give algorithms on calibration and antenna pattern correction (APC) of CELMS. We also describe in detail the principle of microwave transfer among the elements of CELMS, and discuss the method on testing calibration parameters of the system. In addition, the theory and model on correction antenna pattern of CELMS are developed by comparing antenna temperatures by CELMS with those simulated by microwave radiative transfer models. The global distribution of TB is given and the features of TB are analyzed. Our results show rich information included in TB on the properties of lunar regolith, especially the thickness and dielectric constant, which are nearly directly reflected by the differences of TB at day and those at night.

Tracking desertification on the Mongolian steppe through NDVI and field-survey data

Changing environmental and socio-economic conditions make land degradation,a major concern in Central and East Asia.Globally satellite imagery,particularly Normalized Difference Vegetation Index(NDVI)data,has proved an effective tool for monitoring land cover change.This study examines 33 grassland water points using vegetation field studies and remote sensing techniques to track desertification on the Mongolian plateau.Findings established a significant correlation between same-year field observation(line transects)and NDVI data,enabling an historical land cover perspective to be developed from 1998 to 2006.Results show variable land cover patterns in Mongolia with a 16%decrease in plant density over the time period.Decline in cover identified by NDVI suggests degradation;however,continued annual fluctuation indicates desertification
irreversible land cover change
has not occurred.Further,in situ data documenting greater cover near water points implies livestock overgrazing is not causing degradation at water sources.In combination of the two research methods
remote sensing and field surveys
strengthen findings and provide an effective way to track desertification in dryland regions.

Fingerprint of COVID-19 in Arctic sea ice changes

Arctic sea ice plays an essential role in regional and global climate by dynamic processes and feedbacks associated with its high reflectivity, thermal insulation especially in presence of snow cover, and brine rejection [1]. Both observations and model simulations show that Arctic sea ice extent has dramatically declined and thinned in the past few decades [2] in response to global warming and cumulative anthropogenic greenhouse gas(GHG)emissions [3,4].