高纬海区舰船陀螺罗经指向误差的分析与补偿

为客观准确描述其误差规律,对高纬海区陀螺罗经指向稳定性和准确性进行测试和分析。首先,利用船舶在白令海至北极东北航道实测的陀螺罗经指向数据,通过对比高精度GPS光纤罗经指向数据,分析陀螺罗经在北半球高纬地区指向的稳定性和误差分布特性;其次,利用最小二乘法获取陀螺罗经误差拟合曲线和拟合参数,分析拟合效果;最后,利用拟合参数建立高纬海区陀螺罗经指向误差补偿模型,并使用高纬海区陀螺罗经其他指向数据开展误差补偿验证。仿真结果表明:经过误差补偿,陀螺罗经误差在高纬海区的指向误差明显减小,在纬度78.0°N以下海区补偿残差不超过0.8°,满足舰船高纬海区航行的指向需求。

磁罗经北极高纬海区航向误差分析与补偿

针对舰船高纬海区航行时磁罗经指北力减弱,指向精度降低的问题,将船舶在白令海至北极东北航道实测的磁罗经指向数据与高精度GPS光纤罗经指向数据对比,分析舰船磁罗经在北极高纬地区指向的稳定性和自差变化特性,构建误差拟合曲线并基于拟合参数建立北极高纬海区磁罗经指向误差补偿模型,仿真结果表明,通过误差补偿,磁罗经在北极高纬海区的指向误差明显减小,在纬度70°以下海区补偿残差不超过3°,在78°以下海区补偿残差不超过5°,满足舰船北极高纬海区航行时磁罗经指向精度要求。

高纬海区沉积物的高分辨铀系测年:^(230)Th─б_O^(18)地层学

1 序 海洋沉积物提供了地质时期古气候演变的信息。由于钙质有孔虫类的氧同位素组分取决于气候条件,可以用作地层的研究工具(Martjnson等,1987)。δ^(18)O法只能用于有孔虫类是沉积物中常见组成的地域。由干高纬地区水温比较低,这些海域的沉积物常极少含有或不含钙质有孔虫,所以,沉积物年龄的获得只能依靠古地磁、生物地层和放射性核素测年等方法(Herman等,1990)。 高纬地区(挪威─格陵兰海)的深水地层和气候变化之间存在紧密联系是有明显的证据的。与海洋沉积物反映古海洋环境一样,沉积物岩芯测年对于了解古气候演变也具有很大的意义。 过剩^(230)Th法(~230)Thex,是沉积物中非隐含的^(230)Th)可以用来测定高纬地区,如挪威─格陵兰海、弗拉姆海峡和北冰洋等地的上限为30万年的贫钙沉积物的年龄(Scholten等,1990)。^(230)Thex法依赖于水体中溶解^(230)U衰变成^(230)Th的恒定产率。因为^(230)Th是高度粒子活性的,它能在10─40年内从水中移入沉积物(Nozaki等,1987),在沉积物中^(230)Th的衰变过程(半衰期75,200年)可以用于测年目的。

北大西洋高纬度海区湍流热通量对全球增暖的响应

大西洋经向翻转环流(the Atlantic Meridional Overturning Circulation,AMOC)由低纬输送大量热量至高纬度北大西洋海区,并通过热通量由海洋输送给大气,主导了附近区域的气候形态,并对北半球尺度的气候变化产生显著影响。本文根据CMIP5多模式多增暖情景的预估模拟结果,通过与增暖前控制试验的对比发现,全球增暖可导致该海区湍流热通量的减小,且减小的幅度随增暖强度增大,模拟结果与观测一致。进一步研究发现,热通量的减小存在季节差异,冬季的减小幅度远大于夏季。结合淡水扰动试验的分析表明,全球增暖下AMOC强度的减弱导致大西洋经向热输送减少,进而导致高纬度北大西洋海洋向大气的热输送减小。

白令海及北太平洋高纬航线的安全航行

简要介绍白令海及北太平洋高纬度海域的气象海况特征,探讨北太平洋高纬度航线的安全航行和白令海海区航路及进出白令海海峡通道的相关注意事项,并探讨在北太平洋高纬航线遭遇恶劣气象的应对和规避措施。

On Spatiotemporal Characteristics of Sea Fog Occurrence over the Northern Atlantic from 1909 to 2008

In this paper, the International Comprehensive Ocean and Atmosphere Data Set(ICOADS) is utilized to investigate the horizontal distribution of sea fog occurrence frequency over the Northern Atlantic as well as the meteorological and oceanic conditions for sea fog formation. Sea fog over the Northern Atlantic mainly occurs over middle and high latitudes. Sea fog occurrence frequency over the western region of the Northern Atlantic is higher than that over the eastern region. The season for sea fog occurrence over the Northern Atlantic is generally from April to August. When sea fogs occur, the prevailing wind direction in the study area is from southerly to southwesterly and the favorable wind speed is around 8 m s-1. It is most favorable for the formation of sea fogs when sea surface temperature(SST) is 5℃ to 15℃. When SST is higher than 25℃, it is difficult for the air to get saturated, and there is almost no report of sea fog. When sea fogs form, the difference between sea surface temperature and air temperature is mainly-1 to 3℃, and the difference of 0℃ to 2℃ is the most favorable conditions for fog formation. There are two types of sea fogs prevailing in this region: advection cooling fog and advection evaporating fog.

Interdecadal and Interannnual Variabilities of the Antarctic Oscillation Simulated by CAM3

Based on four sets of numerical simulations prescribed with atmospheric radiative forcing and sea surface temperature(SST) forcing in the Community Atmospheric Model version 3(CAM3), the interannual and interdecadal variabilities of the Antarctic oscillation(AAO) during austral summer were studied. It was found that the interannual variability is mainly driven by SST forcing. On the other hand, atmospheric radiative forcing plays a major role in the interdecadal variability. A cooling trend was found in the high latitudes of the Southern Hemisphere(SH) when atmospheric radiative forcing was specified in the model. This cooling trend tended to enhance the temperature gradient between the mid and high latitudes in the SH, inducing a transition of the AAO from a negative to a positive phase on the interdecadal timescale. The cooling trend was also partly weakened by the SST forcing, leading to a better simulation compared with the purely atmospheric radiative forcing run. Therefore, SST forcing cannot be ignored, although it is not as important as atmospheric radiative forcing.

Global Distribution of Thermosteric Contribution to Sea Level Rising Trend

The sea level derived from TOPEX/Poseidon （T/P） altimetry data shows prominent long term trend and inter-annual variability. The global mean sea level rising rate during 1993-2003 was 2.9mm a^-1. The T/P sea level trend maps the geographical variability. In the Northern Hemisphere （15°-64°N）, the sea level rise is very fast at the mid-latitude （20°-40°N） but much slower at the high-latitude, for example, only 0.5 mm a^-1 in the latitude band 40°-50°N. In the Southern Hemisphere, the sea level shows high rising rate both in mid-latitude and high-latitude areas, for example, 5.1 mm a^-1 in the band 40°- 50°S. The global thermosteric sea level （TSL） derived from Ishii temperature data was rising during 1993-2003 at a rate of 1.2 mm a^-1 and accounted for more than 40% of the global T/P sea level rise. The contributions of the TSL distribution are not spatially uniform; for instance, the percentage is 67% for the Northern Hemisphere and only 29% for the Southern Hemisphere （15°-64°S） and the maximum thermosteric contribution appears in the Pacific Ocean, which contributes more than 60% of the global TSL. The sea level change trend in tropical ocean is mainly caused by the thermosteric effect, which is different from the case of seasonal variability in this area. The TSL variability dominates the T/P sea level rise in the North Atlantic, but it is small in other areas, and shows negative trend at the high-latitude area （40°-60°N, and 50°-60°S）. The global TSL during 1945-2003 showed obvious rising trend with the rate of about 0.3 mm a-l and striking inter-annual and decadal variability with period of 20 years. In the past 60 years, the Atlantic TSL was rising continuously and remarkably, contributing 38% to the global TSL rising. The TSL in the Pacific and Indian Ocean rose with significant in- ter-annual and decadal variability. The first EOF mode of the global TSL from Ishii temperature data was the ENSO mode in which the time series of the first mode showed steady rising trend. Among the three oceans, the first mode of the Pacific TSL presented the ENSO mode; there was relatively steady rising trend in the Atlantic Ocean, and no dominant mode in the Indian Ocean.

An improved diagnostic stratocumulus scheme based on estimated inversion strength and its performance in GAMIL2

Based on satellite data and the estimated inversion strength(EIS) derived by Wood et al.(2006), a feasible and uncomplicated stratocumulus scheme is proposed, referred to as EIS scheme. It improves simulation of cloud radiative forcing(CRF) in the Grid-point Atmospheric Model of IAP/LASG version 2(GAMIL2.0) model. When compared with the original lower troposphere stability(LTS) scheme, the EIS scheme reproduces more reasonable climatology distributions of clouds and CRF. The parameterization partly corrects CRF underestimation at mid and high latitudes and overestimation in the convective region. Such improvements are achieved by neglecting the effect of free-tropospheric stratification changes that follow a cooler moist adiabat at middle and high latitude, thereby improving simulated cloudiness. The EIS scheme also improves simulation of the CRF interannual variability. The positive net CRF and negative stratiform anomaly in the East Asian and western North Pacific monsoon regions(EAWNPMR) are well simulated. The EIS scheme is more sensitive to sea surface temperature anomalies(SSTA) than the LTS. Therefore, under the effect of a warmer SSTA in the EAWNPMR, the EIS generates a stronger negative stratiform response, which reduces radiative heating in the low and mid troposphere, in turn producing strong subsidence and negative anomalies of both moisture and cloudiness. Consequent decreases in cloud reflection and shading effects ultimately improve simulation of incoming surface shortwave radiative fluxes and CRF. Because of the stronger subsidence, a stronger anomalous anticyclone over the Philippines Sea is simulated by the EIS run, which leads to a better positive precipitation anomaly in eastern China during ENSO winter.

Global distributions of OH and O_2 (1.27 μm) nightglow emissions observed by TIMED satellite

In order to investigate the global distributions of temporal variations of OH and O2 nightglow emissions,we statistically analyzed their variations with altitude,local time,and season,using the OH and O2 airglow emission rate data observed by the TIMED satellite between 2002 and 2009.The results indicated that the OH nightglow emission was stronger than dayglow emission and the O2 nightglow emission was weaker than dayglow emission.In the tropics,the OH nightglow intensity reached its maximum near midnight;at higher latitudes,the OH nightglow intensities after sunset and before sunrise were much strong.At the equinoxes,the O2 nightglow intensity in the tropics decreased with local time;at the solstices,the local time-latitude distribution of the O2 nightglow intensity had a valley(with weak emission).As for the altitude-latitude distributions of nightglow emission rates,the distribution for OH nightglow at the equinoxes had one peak(with strong emission)at the equator,with a peak height around 85 km;the peak for the March equinox was stronger than that for the September equinox.The distribution for O2 nightglow at the equinoxes had three peaks,lying at 30°in the spring and autumn hemispheres and at the equator,and the peak height at the equator was the lowest.The distributions for both OH and O2 nightglow emissions at the solstices had three peaks.Both nightglow intensities in the tropics had obvious annual and semi-annual variations,the peaks and valleys for semi-annual variations appeared near the equinoxes and solstices,respectively,and the peak at the March equinox was larger than that at the September equinox.The distributions of both OH and O2 nightglow intensities showed a hemispheric asymmetry.

Effect of opening the Drake Passage on the oceanic general circulation:A box model study

The impacts of opening the Drake Passage(DP) on the oceanic general circulation are examined.When the DP is open,wind stress at mid-and high latitudes gives rise to a wind-driven gyre,which induces a meridional heat exchange between mid-and high latitudes in the Southern Ocean.After the opening of the DP,the Antarctic Circumpolar Current(ACC) forms and its associated strong temperature front blocks the heat transport from mid-latitudes to high latitudes.A simple box model is formulated,in which the effects of the wind stress(for the case of DP closed) and the thermal front(for the case of DP open) on the variability of Antarctic Bottom Water(AABW) and North Atlantic Deep Water(NADW) are explored.The sensitivity experiments demonstrate that:(1) When the DP is closed,the enhancement of the wind-driven gyre leads to the decline of AABW formation in the Southern Ocean and the increase of NADW formation in the North Atlantic.As a result,water in high latitudes of the Southern Ocean becomes warmer,so does the bottom water of global ocean.(2) When the DP is open,there is no formation of AABW until the intensity of thermal front along ACC exceeds a threshold value(it is 4.03℃ in our model).Before the formation of AABW,temperature in most of the oceans is higher than that after the formation of AABW,which usually leads to the cooling of high latitudes of the Southern Hemisphere and the bottom water in global ocean.When the strength of the thermal front is lower than the critical value,there is no AABW formation,and temperature in most of the oceans is slightly higher.These results demonstrate that during the opening of the DP,changes in wind stress and the formation of the thermal front in the Southern Ocean can substantially affect the formation of AABW and NADW,thus changing the state of meridional overturning circulation in the global ocean.