The importance of ship log data: reconstructing North Atlantic, European and Mediterranean sea level pressure fields back to 1750

Local to regional climate anomalies are to a large extent determined by the state of the atmospheric circulation. The knowledge of large-scale sea level pressure (SLP) variations in former times is therefore crucial when addressing past climate changes across Europe and the Mediterranean. However, currently available SLP reconstructions lack data from the ocean, particularly in the pre-1850 period. Here we present a new statistically-derived 5° × 5° resolved gridded seasonal SLP dataset covering the eastern North Atlantic, Europe and the Mediterranean area (40°W–50°E; 20°N–70°N) back to 1750 using terrestrial instrumental pressure series and marine wind information from ship logbooks. For the period 1750–1850, the new SLP reconstruction provides a more accurate representation of the strength of the winter westerlies as well as the location and variability of the Azores High than currently available multiproxy pressure field reconstructions. These findings strongly support the potential of ship logbooks as an important source to determine past circulation variations especially for the pre-1850 period. This new dataset can be further used for dynamical studies relating large-scale atmospheric circulation to temperature and precipitation variability over the Mediterranean and Eurasia, for the comparison with outputs from GCMs as well as for detection and attribution studies.     

Description and General Background to Ships' Logbooks as a Source of Climatic Data

Meteorological observations made on board ships prior to 1854 have until now been overlooked in climatological research largely as a result of the lack of rigorous abstraction and treatment criteria. However, the CLIWOC project has shown that millions of potentially valuable observations have been preserved throughout Europe in the many logbooks that were prepared by officers in the navies of the great powers. Moreover these data can be used and treated in a fashion similar to today's ship-based instrumental observations. The most significant logbook collections are from Spain, the UK, the Netherlands and France. This paper describes the main archives where the logbooks can be found and provides an account of their contents and of the manner in which they were set out. The potential of this source is emphasised by the fact that whilst the CLIWOC project abstracted data for 300,000 days, nearly 90% of the European logbook collections have yet to be examined. This paper concludes with a discussion as to the direction of future studies in this important field.     

Atmospheric circulation and storminess derived from Royal Navy logbooks: 1685 to 1750

This paper is concerned with the use of Royal Navy ships’ logbooks for the period 1685 to 1750, thereby embracing the oldest members of this documentary series that extends to the present day. The geographic range of the undertaking is confined to the English Channel and its western approaches where the abundance of logbooks for this period allows for the abstraction of a daily series of wind force and direction data. These are verified and processed for inclusion in a database from which indices are derived for air circulation patterns based on the frequency of winds from north, east, south and west quarters, and of gale frequency, based on the contemporary terminology of wind force. The methods by which the data are abstracted and processed are described, as is the nature of the raw data and source material. The results provide a uniquely detailed insight into the changing patterns of air circulation over this critical period that marked the transition from the depths of the Little Ice Age in the late seventeenth century. Attention is also drawn to the changing nature of gale frequency, which revealed a notable decrease over the study period. Associations between changing circulation patterns and temperature regimes are also explored.     

CLIWOC: A Climatological Database for the World's Oceans 1750–1854

We have compiled a meteorological database over the world's oceans by digitizing data from European ship logbooks of voyages in the period 1750–1854. The observations are carefully reviewed and transformed into quantitative data. The chief contents of the database are wind direction and wind force information, from a period without standardized scales. It is found that the information content of these so-called non-instrumental data is much higher than previously believed. The 105-year CLIWOC database extends existing meteorological world ocean databases like ICOADS back in time by a full century.     

Corrections of Systematic Errors, Data Homogenisation and Climatic Analysis of the Padova Pressure Series (1725-1999)

A short history of the series with daily observations of barometric pressure in Padova (since 1725) is made, with special reference to the types of barometers used, their locations, the types of corrections (which were only partial in the early period), the calibrations and the comparison with primary instruments. The paper also describes the homogenisation of the series and the procedures used to fill the small gaps. The Padova series was compared with previously well investigated series from the ADVICE and IMPROVE projects and especially with the nearby Milan series in order to check its reliability. Trend analysis shows an increase in pressure (some 1 hPa) during the last a hundred year. This trend is a common feature for Northern Italy. An effect of the increased air pressure is a local lowering of the Northern Mediterranean Sea level by 1 cm. The part of the year mostly affected by this increase is from late spring to August and corresponds to an extension of the hot season, characterised by an earlier start, and longer duration of the Azores Anticyclone. This reduces the penetration of the Atlantic disturbances in the Northern Mediterranean and the precipitation associated with the passage of fronts. This change is associated with an increase in thermoconvective activity with thunderstorms and heavy precipitation. This explains why, in the last decades, the annual total amount of precipitation is slightly decreased and at the same time the frequency of intense rainfall is increased. Moreover, a comparison of the day-to-day pressure variability with the Western Mediterranean Oscillation (WeMO) indicates a significant positive correlation during the late autumn-early winter period. An increase of the WeMO index means a strengthening of the baric dipole from Azores to Northern Italy, that could be explained by a deepening of the cyclonic circulation over northern Italy from November to January.     

青藏高原大气热源与江淮梅雨异常的关系

利用江淮流域1954\_2001年梅雨量资料和同期内美国NCEP/NCAR 逐日高度场、 风场、 比湿场和地面气压场再分析资料, 网格距为2.5°×2.5°。采用模糊聚类、 EOF分解、 合成分析、 SVD分解等方法, 详细讨论了青藏高原大气热源与江淮梅雨的关系。结果表明： 梅雨量区域指数能很好地揭示江淮流域梅雨量的丰枯, 高原大气热源大致以90°E为界, 可分为高原东部型和西部型; 高原大气热源与梅雨量存在显著相关关系, 高原大气热源东部型与江淮梅雨量呈显著正相关关系, 西部型与梅雨量呈显著负相关关系、说明高原大气热源东部型增强, 西部型减弱, 江淮梅雨量异常偏多。高原大气热源东部型减弱, 西部型增强, 江淮梅雨量异常偏少; 反之亦然、SVD分解结果与合成分析的结果完全一致。     

A global assessment of the human pressure on the world's lakes

Millions of humans across the globe depend on lakes for numerous ecosystem services. Furthermore, humans use lakes as a food source and for a multitude of economic activities. Lakes are also essential to a plethora of taxa that rely on them for survival. Yet, despite the importance of lakes, we still lack an assessment of the extent lakes worldwide are being influenced by anthropogenic activities. In this study, I use the global database of lakes, the human footprint index from 1993 and 2009, and the more recent human modification index to measure the human pressure on the world's lakes. I found that one-third of the lakes are under considerable pressure. However, during the 16-year period examined, human pressure had increased in only 16% of the lakes, while it remained unchanged in 66%, and has even decreased in 18%. These patterns, though, were not uniform across the globe. Many lakes within tropical and subtropical regions, particularly in Africa—but also in South America and Asia—experienced sizeable increases in human pressure. Moreover, the percentage of lakes within Key Biodiversity Areas in which the human pressure had increased was three times larger the overall number. Although increases in human pressure were lower in lakes within protected areas—compared to lakes outside—there were numerous exceptions, particularly in the tropics. To protect biodiverse lakes in regions where human pressure is intensifying, it is important to improve the effectiveness of the protected areas and to address the socioeconomic factors driving the increases in human pressure.     

A Reassessment of Historical Atlantic Basin Tropical Cyclone Activity, 1700–1855

The chronological table of Atlantic basin tropical cyclones produced by Andrés Poey in 1855 is the foundation stone for present-day knowledge of historical Atlantic tropical cyclone activity. Subsequent researchers have used his table and built upon it, rejecting some of his entries, modifying others, and accepting the rest. A re-analysis of the 1700–1855 portion of Poey's original published list was made using historical newspaper accounts, weather diaries, and ships' logbooks. Of the 348 separate entries in Poey's original list, 149 were rejected and 198 accepted. Due to errors in dating and location, and the linking of separate entries as parts of the same storm, only 170 of the 198 accepted entries are unique storms. Thirteen undated storms of the remaining 170 are now dated. The authorities cited by Poey vary in their reliability. Of those cited 10 or more times, there was an average of one incorrect citation for every 3.1 correct citations. The most and least reliable authorities used by Poey are identified. An updated corrected chronology from all published sources is presented and includes 383 unique storms through 1855.     

二阶闭合模式在污染气象学中的某些应用

本文采用二阶闭合的湍流边界层模式,进行一系列数值试验以模拟边界层中连续线源的扩散状况。试验表明:无论在稳定的或不稳定的边界层中,高源的扩散能力都低于低源;在稳定层中,粗糙地表上的大气扩散能力高于光滑表面;在相同风速和地表净辐射情况下,粗糙表面上的大气扩散能力反而低于光滑表面;对流边界层中存在反梯度输送,因而K理论的应用受到限制。试验还表明,修正的Kazanski-Monin参数可能比Monin-Obukhov长度更能反映大气的扩散能力。     

Spatial and temporal changes in aridity index in northwest China: 1960 to 2010

Northwest China is the driest region in China and the regional climate fluctuated dramatically during the last century. Aridity index, as the ratio between potential evapotranspiration and precipitation, is a good indicator to represent regional climate character. In this study, the change and attribution of the aridity index was investigated in northwest China using the observed climate data from 80 national meteorological stations during 1960–2010. The spatial and temporal variabilities of the aridity index shows that the annual aridity index decreased significantly (P?<?0.05) by 0.048 year^?1, indicating that northwest China became wetter from 1960 to 2010. A differentiation equation method was used to attribute the change in aridity index to climate variables. The results indicate that the aridity index was most sensitive to the change in precipitation, followed by vapor pressure, solar radiation, wind speed, and air temperature. Increase in air temperature should have led to an increase in aridity index, but this effect had been offset by the increase in precipitation and vapor pressure and the decrease in wind speed. Increasing precipitation, which contributed 91.7 % of the decrease in the aridity index, was the dominant factor to the decrease in the aridity index in northwest China from 1960 to 2010.     

对流层顶气压与气温的年(代)际变率研究:冬季特征

利用NCEP／NCAR再分析月平均对流层顶气压、气温资料，研究了1979-2002年冬季全球对流层顶气压、气温的年际和年代际变率。选取了冬季对流层项变率最大的区域来定义气压指数、气温指数。通过分析得到：（1）全球对流层项气压、气温随纬度的增加而增高，但在整个热带地区和高纬度地区对流层顶气压、气温的分布较均匀。在分析时段内全球平均的对流层顶气压呈下降趋势，气温呈降低趋势。这些从全球资料得到的结果支持了已有的从部分探空资料所得到的结果。（2）对流层顶变率最大值出现在北半球的副热带地区，最小值出现在低纬度地区。气压指数和气温指数显示出准13a及准3～6a的周期。在1992年以前准3a的周期变化较强，1989年后准6a较强，显示出年际变化的年代际差异。对流层项气压与对流层顶气温在全球大部分地区都呈显著正相关，但在热带和副极地的部分地区相关较弱。对流层顶气压与对流层平均气温在全球大部分地区都呈显著负相关，但在极地地区有正相关关系，显示了对流层顶与对流层内部变化关系的复杂性。     

A new index for variations in the position of the South Pacific convergence zone 1910/11–2011/2012

Quality controlled and recently homogenised mean sea level pressure records for the South Pacific are used to specify the location and variability of the South Pacific convergence zone (SPCZ) during the austral warm season (November–April). The SPCZ is the world’s largest rainfall band during the austral summer, when it dominates the climate of the South Pacific. A new index called the South Pacific convergence zone index (SPCZI) is derived, and is shown to be coherent with changes in low level wind convergence associated with the SPCZ. This index replaces the earlier SPCZ position index because it uses higher quality mean sea level pressure data than the superseded index and extends the time series further forward in time. The SPCZI allows interannual to decadal variability in the climate of the South Pacific to be tracked for more than a century from 1910/1911 to 2011/2012. During El Niño episodes the SPCZ is displaced by about 1°–3° east, and La Niña events 1°–3° west of the mean position on average. The index indicates a striking movement eastward for the period 1977/78–1998/99, compared with 1944/45–1976/77 in association with the Interdecadal Pacific oscillation (IPO). The eastward movement of the SPCZ in the late twentieth century is related to significant precipitation trends in the South Pacific region. Since 1998/99 the SPCZ has regressed westward with the negative phase change of the IPO. The long-term trend in the SPCZI is very small relative to the interannual to decadal variability and is not statistically significant, suggesting that there has been little overall change in the mean position of the SPCZ over the past century.     

Comparison of the streamflow sensitivity to aridity index between the Danjiangkou Reservoir basin and Miyun Reservoir basin, China

The central route of China’s South-to-North Water Diversion Project would divert water from the Danjiangkou Reservoir basin (DRB) to Beijing beginning in the year 2014. The current main surface water source for Beijing is the Miyun Reservoir basin (MRB). The observed streamflows into the DRB and the MRB decreased significantly due to climatic variation and human activities from 1960 to 2005. The climate elasticity method is widely used to quantitatively separate the impacts of climatic variation and human activities on streamflow. One of the uncertainties of the method is that the impacts of changes in precipitation and potential evapotranspiration on streamflow are separated with the assumption that they are independent. However, precipitation and potential evapotranspiration are not totally independent. Aridity index, as the ratio between potential evapotranspiration and precipitation, could be considered as the representative indicator of climatic variation. In this study, the sensitivity of streamflow to aridity index is evaluated to assess the impact of climatic variation on streamflow in the DRB and the MRB. The result shows that streamflow in the MRB is more sensitive to climatic variation than that in the DRB. However, the effective impact of aridity index on streamflow is the product of the sensitivity and the change rate of aridity index. The attribution results show that change in aridity index contributed 68.8 % of the decrease in streamflow in the DRB while it contributed 31.5 % of the decrease in streamflow in the MRB. This indicated that the impact of climatic variation was the main reason of decrease in streamflow in the DRB while human activities such as increasing water consumption and land use change were the main reasons of decreasing streamflow in the MRB.     

东亚季风及台风过程与臭氧含量变化的关系分析

文中用2001~2015年东亚区域的气压场和对流层顶臭氧含量的资料,选用并计算了最能代表东亚地区季风活动的两种指数,应用统计分析和个例分析的方法,对东亚地域内季风运动及台风过程与臭氧浓度变化的相关性进行了分析。得到如下结论:东亚的夏季风强度指数SMC与对流层顶臭氧含量两者在40°~50°N的高纬度地区有明显的正相关关系,赤道附近存在着负相关区。东亚IWT冬季风指数与对流层顶臭氧含量在南海—西北太平洋的海域有很好的正相关。在对流层上层受台风中心强上升气流影响最频繁的地区臭氧浓度低,而受到台风外围下沉气流影响最多的地区臭氧浓度高。      

Nonlinear relation of the Arctic oscillation with the quasi-biennial oscillation

A nonlinear principal component analysis (NLPCA) is applied to a set of monthly mean time series from January 1956 to December 2007 consisting of the Arctic oscillation (AO) index derived from 1,000-hPa geopotential height anomalies poleward of 20°N latitude and the zonal winds observed at seven pressure levels between 10 and 70?hPa in the equatorial stratosphere to investigate the relation of the AO with the quasi-biennial oscillation (QBO). The NLPCA is conducted using a new, compact neural network model. The NLPCA modeling of the dataset of the AO index and QBO winds offers a clear picture of the relation between the two oscillations. In particular, the phase of covariation of the oscillations defined by the two nonlinear principal components of the dataset progresses with a predominant 28.4-month periodicity. This predominant cycle is modulated by an 11-year cycle. The variation of the AO index with the QBO phase also shows that the average AO index is positive when the westerly QBO phase descends past 30?hPa and, conversely, the average AO index is negative when the easterly QBO phase descends past 30?hPa. This relationship is evident during the boreal cold season from November to April but non-existent during the boreal warm season from May to October.     

Witnessing North Atlantic westerlies variability from ships’ logbooks (1685–2008)

A monthly index based on the persistence of the westerly winds over the English Chanel is constructed for 1685–2008 using daily data from ships’ logbooks and comprehensive marine meteorological datasets. The so-called Westerly Index (WI) provides the longest instrumental record of atmospheric circulation currently available. Anomalous WI values are associated with spatially coherent climatic signals in temperature and precipitation over large areas of Europe, which are stronger for precipitation than for temperature and in winter and summer than in transitional seasons. Overall, the WI series accord with the known European climatic history, and reveal that the frequency of the westerlies in the eastern Atlantic during the twentieth century and the Late Maunder Minimum was not exceptional in the context of the last three centuries. It is shown that the WI provides additional and complementary information to the North Atlantic Oscillation (NAO) indices. The analysis of WI series during the industrial era indicates an overall good agreement with the winter and high-summer NAO, with the exception of several multidecadal periods of weakened correlation. These decoupled periods between the frequency and the intensity of the zonal flow are interpreted on the basis of several sources of non-stationarity affecting the centres of the variability of the North Atlantic and their teleconnections. Comparisons with NAO reconstructions and long instrumental indices extending back to the seventeenth century suggest that similar situations have occurred in the past, which call for caution when reconstructing the past atmospheric circulation from climatic proxies. The robustness and extension of its climatic signal, the length of the series and its instrumental nature make the WI an excellent benchmark for proxy calibration in Europe and Greenland.     

用增强显示云图确定热带气旋强度的方法

文章介绍了用增强显示红外云图确定热带气旋强度的方法。利用1983—1988年GMS增强显示云图资料，对中央气象台使用的《用地球同步气象卫星红外云图估计热带气旋强度》的方法中的云特征指数进行了修改与调整，增加了眼区的温度、中心强对流云区和螺旋云带的云顶温度等新的云特征因子。经统计、拟合，得到云特征指数与热带气旋中心附近最大风速、最低海平面气压的对应关系，给出了计算热带气旋强度的人-机交互方法流程，此方法对各种强度的热带气旋都能客观地计算其强度，使用简便，且精度满足业务应用要求。     

Local and synoptic mechanisms causing Southern California’s Santa Ana winds

The atmospheric conditions that lead to strong offshore surface winds in Southern California, commonly referred to as Santa Ana winds, are investigated using the North American Regional Reanalysis and a 12-year, 6-km resolution regional climate simulation of Southern California. We first construct an index to characterize Santa Ana events based on offshore wind strength. This index is then used to identify the average synoptic conditions associated with Santa Ana events—a high pressure anomaly over the Great Basin. This pressure anomaly causes offshore geostrophic winds roughly perpendicular to the region’s mountain ranges, which in turn cause surface flow as the offshore momentum is transferred to the surface. We find, however, that there are large variations in the synoptic conditions during Santa Ana conditions, and that there are many days with strong offshore flow and weak synoptic forcing. This is due to local thermodynamic forcing that also causes strong offshore surface flow: a large temperature gradient between the cold desert surface and the warm ocean air at the same altitude creates an offshore pressure gradient at that altitude, in turn causing katabatic-like offshore flow in a thin layer near the surface. We quantify the contribution of “synoptic” and “local thermodynamic” mechanisms using a bivariate linear regression model, and find that, unless synoptic conditions force strongly onshore winds, the local thermodynamic forcing is the primary control on Santa Ana variability.