Retrieving capillary-gravity wave spectrum from polarimetric microwave radiation of ocean surface     

YIN XiaoBin  WANG ZhenZhan & LIU YuGuang Center for Space Science  Applied Research  Chinese Academy of Sciences  Beijing  China  Physical Oceanography Laboratory  Ocean University of China  Qingdao 《中国科学:地球科学(英文版)》2010,(6)

A new simple two-scale model on the polarimetric microwave emission of ocean surface is derived at first, which can be ex-pressed as an integral of weighting functions (M0 and M2) and ocean surface curvature spectrum coefficients (C0 and C2). This provides a simple way to investigate the effect of curvature spectrum on ocean emission. It is found that ocean waves with wavelengths both comparable to and much greater than the electromagnetic wavelength can contribute to the harmonics of ocean surface microwav...  相似文献   

藏北高原典型季节冻土区和多年冻土区小气候特征对比研究   总被引：4，自引：2，他引：2  

谷良雷  姚济敏  胡泽勇  赵林 《冰川冻土》2016,38(6):1482-1490

利用藏北高原位于季节冻土区的那曲BJ站和多年冻土区的唐古拉站2008年气象要素观测资料,对两站点的小气候特征进行了分析和对比,得到以下结论：那曲BJ站最大冻结深度可达1.5m左右;唐古拉站活动层最大融化深度超过了3.0m。两站的气温、比湿、降雨和积雪均有明显的季节变化;降雨和比湿均是5-10月较大,其他时段较小;积雪均基本集中在1-3月和10-12月。各层土壤温度及日变幅、温度的月均值和月最高/低值及月较差、比湿的月均值和瞬时最大值、风速瞬时最大值均是那曲BJ站大于唐古拉站。那曲BJ站与唐古拉站的风速、气温、比湿的年平均值分别是4.73m·s^-1、-1.34℃、3.96g·kg^-1和4.02m·s^-1、-5.80℃、3.25g·kg^-1,年降雨量和积雪日数分别为590.50mm、114d和405.27mm、135d,两站5-10月的降雨量分别占全年降雨量的96.20%和86.55%。两站在2月初和11月初由于较大降雪均出现了气温陡降的现象,最大积雪日均出现在11月,日最大积雪深度BJ站小于唐古拉站。典型晴天日,那曲BJ站在冬季而唐古拉站在冬春季节风速日变化明显;比湿日变化夏秋季节较冬春季节明显。  相似文献   

四川盆地区表层土壤湿度时空变化特征分析   总被引：2，自引：0，他引：2  

邓彪  肖天贵 《成都信息工程学院学报》2013,28(1):49-55

分析常年土壤干湿状况及其影响因子,是监测评价四川盆地区土壤水分变化的基础,有利于农业干旱防灾减灾.利用四川盆地区农业气象站近17年0～20cm的逐句土壤湿度观测资料,运用旋转正交函数分解(REOF)、相关分析、趋势倾向率分析等方法,对四川盆地区表层土壤相对湿度的时空变化特征进行分析,并分区域选取代表站建立表层土壤湿度与气温、降水量、日照时数的多元回归方程.结果表明,盆地表层土壤相对湿度空间分布大致是从南到北逐渐减小;年际变化呈现弱的上升趋势;常年季节变化呈双峰型特点,秋季高,春季低,夏季波动明显,初夏高盛夏低;表层土壤干湿状况总体呈现出冬春季相对偏干、夏秋季相对偏湿的季节变化.盆地表层土壤湿度变化与气温、日照显著负相关,与降水显著正相关性,气温、日照、降水因子分别对盆地东北部、中南部、西北部表层土壤湿度变化影响大.  相似文献   

Local variability in temperature, humidity and radiation in the BaekduDaegan Mountain protected area of Korea   总被引：1，自引：1，他引：0  

CHAE Heemun  LEE Hyunju  LEE Sangsin  CHEONG Yukyong  UM Gijeung  MARK Bryan  PATRICK Nathan 《山地科学学报》2012,9(5):613-627

A novel embedded sensor network records changes in key climatic-environmental variables over a range of altitude in the BaekduDaegan Mountain (BDM) of Gangwon Province in Korea, a protected mountain region with unique biodiversity undergoing climate change research. The investigated area is subdivided into three horizontal north-south study areas. Three variables, temperature (T, ℃), relative humidity (RH, %), and light intensity (LI, lumens m -2 , or lux, lx), have been continuously measured at hourly intervals from June, 2010 to September, 2011 using HOBO H8 devices at 10 fixed study sites. These hourly observations are aggregated to monthly, seasonal and annual mean values, and results are summarized to inaugurate a long-term climate change investigation. A region wide T difference in accordance with altitude, or lapse rate, over the interval is calculated as 0.4℃100 m -1 . T lapse rates change seasonally, with winter lapse rates being greater than those of summer. RH is elevated in summer compared to other seasons. LI within forestland is lower during summer and higher during other seasons. The obtained results could closely relate to the vegetation type and structure and the terrain state since data loggers were located in forestland.  相似文献   

微波炉法测定遗址土含水率的可靠性研究   总被引：1，自引：0，他引：1  

张虎元  张秋霞  李敏 《岩土力学》2012,33(Z2):65-0070

古代土遗址病害发展与土的含水率变化密切相关,但土遗址保护现场快速准确测定土的含水率不是一件容易的事。选择遗址土、含盐土、黄土等进行对比试验,研究分析微波炉烘干法（简称微波炉法）测遗址土含水率结果的可靠性。在测定试验土样界限含水率和易溶盐含量的基础上,对比分析微波炉法、烘箱法两种方法测定土含水率的误差来源。试验结果表明,土的塑性对微波炉法的测定有一定影响,但测定误差均在2%以内;土的含盐量影响水分的蒸发速度,不影响微波炉法的测定结果;微波法测定遗址土含水率准确,且具有快速、便捷等优势,值得在土遗址保护工程中推广使用。  相似文献   

A new method of measuring the cluster peculiar velocity power spectrum     

Pengjie Zhang  Hume A. Feldman  Roman Juszkiewicz  Albert Stebbins 《Monthly notices of the Royal Astronomical Society》2008,388(2):884-888

We propose to use spatial correlations of the kinetic Sunyaev–Zeldovich (KSZ) flux as an estimator of the peculiar velocity power spectrum. In contrast with conventional techniques, our new method does not require measurements of the thermal SZ signal or the X-ray temperature. Moreover, this method has the special advantage that the expected systematic errors are always subdominant to statistical errors on all scales and redshifts of interest. We show that future large sky coverage KSZ surveys may allow a peculiar velocity power spectrum estimates of an accuracy reaching ∼10 per cent.  相似文献   

A low cosmic microwave background variance in the Wilkinson Microwave Anisotropy Probe data     

C. Monteserín  R. B. Barreiro  P. Vielva  E. Martínez-González  M. P. Hobson  A. N. Lasenby 《Monthly notices of the Royal Astronomical Society》2008,387(1):209-219

We have estimated the cosmic microwave background (CMB) variance from the three-year Wilkinson Microwave Anisotropy Probe ( WMAP ) data, finding a value which is significantly lower than the one expected from Gaussian simulations using the WMAP best-fitting cosmological model, at a significance level of 98.7 per cent. This result is even more prominent if we consider only the North ecliptic hemisphere (99.8 per cent). Different analyses have been performed in order to identify a possible origin for this anomaly. In particular, we have studied the behaviour of single-radiometer and single-year data as well as the effect of residual foregrounds and 1/f noise, finding that none of these possibilities can explain the low value of the variance. We have also tested the effect of varying the cosmological parameters, finding that the estimated CMB variance tends to favour higher values of n _s than the one of the WMAP best-fitting model. In addition, we have also tested the consistency between the estimated CMB variance and the actual measured CMB power spectrum of the WMAP data, finding a strong discrepancy. A possible interpretation of this result could be a deviation from Gaussianity and/or isotropy of the CMB.  相似文献   

Determining the motion of the Solar system relative to the cosmic microwave background using Type Ia supernovae     

Christopher Gordon  Kate Land  An&#;e Slosar 《Monthly notices of the Royal Astronomical Society》2008,387(1):371-376

We estimate the Solar system motion relative to the cosmic microwave background using Type Ia supernovae (SNe) measurements. We take into account the correlations in the error bars of the SNe measurements arising from correlated peculiar velocities. Without accounting for correlations in the peculiar velocities, the SNe data we use appear to detect the peculiar velocity of the Solar system at about the 3.5σ level. However, when the correlations are correctly accounted for, the SNe data only detect the Solar system peculiar velocity at about the 2.5σ level. We forecast that the Solar system peculiar velocity will be detected at the 9σ level by GAIA and the 11σ level by the Large Synoptic Survey Telescope. For these surveys, we find the correlations are much less important as most of the signal comes from higher redshifts where the number density of SNe is insufficient for the correlations to be important.  相似文献   

Mixed three-point correlation functions of the non-linear integrated Sachs–Wolfe effect and their detectability     

B. M. Schäfer 《Monthly notices of the Royal Astronomical Society》2008,388(3):1394-1402

In this paper, I investigate the family of mixed three-point correlation functions  〈τ ^q γ^{3− q} 〉, q = 0, 1, 2  , between the integrated Sachs–Wolfe (iSW) temperature perturbation τ and the galaxy overdensity γ as a tool for detecting the gravitational interaction of cosmic microwave background (CMB) photons with the potentials of non-linearly evolving cosmological structures. Both the iSW-effect and the galaxy overdensity are derived in hyperextended perturbation theory to second order and I emphasize the different parameter sensitivities of the linear and non-linear iSW-effect. I examine the configuration dependence of the relevant bispectra, quantify their sensitivities and discuss their degeneracies with respect to the cosmological parameters  Ω_m, σ₈, h   and the dark energy equation of state parameter w . I give detection significances for combining Planck CMB data and galaxy sample of a survey like Dark UNiverse Explorer (DUNE) by using a quadratic approximation for the likelihood with Λ cold dark matter (ΛCDM) as the fiducial cosmology: the combination of Planck with DUNE should be able to reach a cumulative signal-to-noise ratio of ≃0.6 for the bispectrum  〈τγ²〉  up to ℓ= 2000, which is too weak to be detected. The most important noise source is the primary CMB fluctuations as the Poisson noise in the galaxy number density is almost negligible for a survey like DUNE.  相似文献   

华东高温期的大气环流特征分析   总被引：4，自引：2，他引：4  

史军  崔林丽  周伟东 《热带气象学报》2009,25(6):753-759

利用NCEP/NCAR再分析资料和地面气象站点资料,对1951—2005年华东高温日数较多（少）月和高温过程各阶段的500 hPa位势高度、850 hPa温度和相对湿度及700 hPa垂直速度的环流特征进行对比分析。结果表明：在高温日数较多月,副高西伸,850 hPa温度较高而相对湿度较低,华东中南部下沉气流明显,华东多为位势高度、温度和垂直速度正距平及相对湿度负距平;而在高温日数较少月,副高东退,850 hPa温度较低而相对湿度较高,整个华东为上升气流,并为位势高度、温度和垂直速度负距平及相对湿度正距平。与高温前期和衰退期相比,高温盛期副高北抬西进,华东850 hPa温度较高而相对湿度较低,华东南部下沉气流强盛,各要素距平值增加,多数要素距平中心移向华东或其周边。高温间断期则比盛期各要素距平减弱。大气环流要素场及其距平场的变动可以作为预报华东7—8月高温日数多寡和高温进程的参考依据。  相似文献