A Method for Increasing the Turbulent Kinetic Energy in the Mellor–Yamada–Janjić Boundary-Layer Parametrization

A method for enhancing the calculation of turbulent kinetic energy in the Mellor–Yamada–Janjić planetary boundary-layer parametrization in the Weather Research and Forecasting numerical model is presented. This requires some unconventional selections for the closure constants and an additional stability dependent surface length scale. Single column model and three-dimensional model simulations are presented showing a similar performance with the existing boundary-layer parametrization, but with a more realistic magnitude of turbulence intensity closer to the surface with respect to observations. The intended application is an enhanced calculation of turbulence intensity for the purposes of a more accurate wind-energy forecast.     

Method for detection of direction and speed of cloud propagation based on the structure of cloudiness self-radiation within the range of 8–13 μm

The method for determining the direction and speed of cloud propagation is presented. The method is based on the cloud field self-radiation within the range of 8?C13 ??m using an automated wide-panoramic scanning system for objective parameterization of the form and cloud amount during the day- and nighttime. The proposed method is based on pairwise comparison of neighboring frames and calculation of shift direction.     

Phosphorus demand for the 1970–2100 period: A scenario analysis of resource depletion

The phosphorus (P) cycle has been significantly altered by human activities. For this paper, we explored the sustainability of current P flows in terms of resource depletion and the ultimate fate of these flows. The analysis shows that rapid depletion of extractable phosphate rock is not very likely, in the near term. Under best estimates, depletion would be around 20–35%. In worst case scenarios, about 40–60% of the current resource base would be extracted by 2100. At the same time, production will concentrate in Asia, Africa and West Asia, and production costs will likely have increased. As there are no substitutes for phosphorus plant nutrients in agriculture, arguably even partial depletion of P resources may in the long run be relevant for the sustainability of agriculture. Consumption trends lead to large flows of phosphorus to surface water and a considerable build-up of phosphorus in agricultural soils in arable lands. This may allow a reduction in future P fertiliser application rates in crop production. Results also indicate a global depletion of P pools in soils under grassland, which may be a threat to ruminant production.     

A Non-Linear Dynamical–Statistical Model for Reconstruction of the Air–Sea Element Fields in the Tropical Pacific Ocean

Aiming at tackling the difficulty in establishing a sea surface temperature (SST) dynamical model, this study develops a non-linear dynamical–statistical model of SST fields and their correlative factors based on Genetic Algorithms (GA) and the dynamical system reconstruction idea, which greatly improves the El Niño–Southern Oscillation (ENSO) forecast model. Using Hadley SST data, sea surface wind (SSW) and sea level pressure (SLP) data from the National Centers for Environmental Prediction-National Center for Environmental Research (NCEP-NCAR), with empirical orthogonal function (EOF) time-space for reconstruction, we carry out numerical integral forecasting experiments for SST, SSW, and SLP fields. By statistical analysis of the forecasting experiments, we find that forecasts for less than 25 months perform better than longer term forecasts. Based on the model, we forecast SST, SSW, and SLP fields in September, October, and November 2014 and predict a weak La Niña event. This study explores a novel method for the complex atmosphere–ocean system.     

GHOST – A Novel Airborne Gas Chromatograph for In Situ Measurements of Long-Lived Tracers in the Lower Stratosphere: Method and Applications

A novel fully-automated airborne gas chromatograph for in situmeasurements of long-lived stratospheric tracers hasbeen developed, combining the high selectivity of a megabore PLOTcapillary column with recently developed sampling and separationtechniques. The Gas cHromatograph for theObservation of Stratospheric Tracers (GHOST)has been successfully operated during three STREAM campaigns(Stratosphere TRoposphere Experiment byAirborne Measurement) onboard a Cessna Citation IIaircraft in two different modes: Either N₂O andCF₂Cl₂(CFC-12) or CFC-12 and CFCl₃ (CFC-11) have been measuredsimultaneously, with a time resolution of 2 min for both modes.Under flight conditions the instrument precision (1) forthese species is better than 0.9%, and the accuracy(1) is better than 2.0% of the tropospheric values ofall measured compounds. The detection limits (3) arebelow 28 ppb for N₂O, 14 ppt for CFC-12, and 8 ppt forCFC-11, respectively, i.e., well below 10 % of the troposphericvalues of all measured compounds. Post-mission optimization of thechromatographic separation showed a possible enhancement of thetime resolution by up to a factor of 2, associated with acomparable increase in precision and detection limit. As test ofactual performance of GHOST results from an in-flight N₂Ointercomparison with a tunable diode laser absorptionspectrometer (TDLAS) are presented. They yield an excellentagreement between both instruments. Furthermore, on the basis ofthe hitherto most extensive set of upper tropospheric and lowerstratospheric data, the relative stratospheric N₂2O lifetime isre-assessed. When referenced to the WMO reference CFC-11 lifetimeof 45 ± 7 years an N₂O lifetime of 91 ± 15 yearsis derived, a value substantially smaller than the WMO referencelifetime of 120 years. Moreover, this value implies astratospheric N₂O sink strength of 16.3 ± 2.7 Tg (N)yr^–1 which is 30% larger than previous estimates.     

The impact of urbanization on water vulnerability: A coupled human–environment system approach for Chennai,India

While there is consensus that urbanization is one of the major trends of the 21^st century in developing countries, there is debate as to whether urbanization will increase or decrease vulnerability to droughts. Here we examine the relationship between urbanization and water vulnerability for a fast-growing city, Chennai, India, using a coupled human–environment systems (CHES) modeling approach. Although the link between urbanization and water vulnerability is highly site-specific, our results show some generalizable factors exist. First, the urban transformation of the water system is decentralized as irrigation wells are converted to domestic wells by private individuals, and not by the municipal authority. Second, urban vulnerability to water shortages depends on a combination of several factors: the formal water infrastructure, the rate and spatial pattern of land use change, adaptation by households and the characteristics of the ground and surface water system. Third, vulnerability is dynamic, spatially variable and scale dependent. Even as household investments in private wells make individual households less vulnerable, over time and cumulatively, they make the entire region more vulnerable. Taken together, the results suggest that in order to reduce vulnerability to water shortages, there is a need for new forms of urban governance and planning institutions that are capable of managing both centralized actions by utilities and decentralized actions by millions of households.     

A weakly coupled data assimilation system of a coupled physical–biological model for the northeastern South China Sea

南海东北部沿岸海域在每年夏季都存在显著的物理过程(如上升流,珠江冲淡水)和活跃的生物过程,这些基本的物理场和生物场要素对沿岸海域的研究起关键作用。本文在一适应于南海东北部的物理生物耦合模式的基础上建立了一个弱约束的EnOI耦合同化系统。开展的SST同化试验结果表明,物理过程存在合理的响应,且近海上升流区的海洋生态变量对物理变量的同化也有响应。     

A comparison of global tropospheric teleconnections using observed satellite and general circulation model total ozone column data for 1979–91

 The total ozone column is well correlated with tropospheric fields such as the heights of the upper tropospheric geopotential surfaces and thus it can provide useful information on temporal variability in the troposphere. The global availability of long period satellite measurements of the total ozone column, taken by the TOMS instruments since 1978, provides a valuable and independent data set for use in studies of seasonal and interannual climate variability. In this study, the global low-frequency seasonal teleconnections in the observed TOMS data from 1979–91 have been investigated using seasonal teleconnectivity maps and empirical orthogonal function analysis. They have also been compared with the results from a simulation made with the atmospheric GCM at Météo-France, having prescribed observed sea surface temperatures for the same period. In the observed total ozone, strong ENSO-related wave number one longitudinal dipole patterns are seen in both the tropics and in the Southern Hemisphere extratropics. The model shows much weaker variability in total ozone yet appears to be able to capture similar teleconnection patterns in the tropics related to ENSO. In the SH extratropics, the model total ozone shows a strong wave number 3 response rather than the wave number one dipole seen in the observations. A wave number 3 response is also evident in the 200 hPa geopotential height simulated by the model and in the NCEP analysis, and is consistent with the response in a linearised barotropic model forced in the Indonesian region. The different responses in the modelled and observed total ozone, suggest that tropopause effect is not the major factor in the SH extratropics, and it is likely that horizontal ozone transport also plays a role in this region. Despite a generally poor simulation of the zonal mean total ozone, the model was able to capture the anomalous strengthening of the SH stationary waves during austral spring of 1988, related to an intense stratosphere sudden warming. Received: 21 October 1996 / Accepted: 11 September 1997     

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.     

Virtual water ‘flows’ of the Nile Basin, 1998–2004: A first approximation and implications for water security

This paper interprets an initial approximation of the ‘trade’ in virtual water of Nile Basin states in terms of national water security. The virtual water content (on the basis of weight) of select recorded crop and livestock trade between 1998 and 2004 is provided, and analysed for each state separately, for the Southern Nile and Eastern Nile states as groups, and for the basin states as a whole. To the extent that the datasets allow, the distinction between rainfed and irrigated production is maintained. During the period under study, Nile Basin states ‘exported’ about 14,000 Mm³ of primarily rainfed-derived virtual water outside of the basin annually and ‘imported’ roughly 41,000 Mm³/y. The ‘imports’ are considered to have played a key role in filling the freshwater deficits of Egypt and Sudan, and represent a third of the flow of the Nile River itself. Analysis of food trade within the basin shows that the equivalent of small rivers of water used to raise coffee and tea ‘flow’ from the highlands around Lake Victoria to Egypt and Sudan. Because the bulk of these ‘flows’ derive from rainfed agriculture, the virtual water ‘traded’ annually between the Nile Basin states is not considered to represent a significant demand on the water resources of the basin, nor to significantly remedy the freshwater deficits of the arid basin states. The importance of soil water and rainfed farming is in improving water security is highlighted. The limitations and merits of the inter-state basin-wide approach are also discussed. By highlighting the magnitude of water leaving and entering states in its virtual form, the approach obliges policy-makers to think beyond the basin and reconsider the concept of water security within broader political, environmental, social and economic forces.     

Tree-ring reconstruction of summer temperature for A.D. 1475–2003 in the central Hengduan Mountains, Northwestern Yunnan, China

Development of long tree-ring records is an important task in paleoclimate studies. Here we presented a five-century long reconstruction of summer (June to August) temperature based on a tree ring-width chronology of Picea brachytyla var. complanata originating from the Hengduan Mountains of China. Climate-growth response analysis showed that summer temperature was the main climatic factor limiting tree-ring growth in the study area. The reconstructed summer temperature accounted for 47.6% of the variance in actual temperature during their common period A.D. 1958–2002. Analysis of the temperature reconstruction showed that major warm periods occurred in the A.D. 1710s–1750s, 1850s, 1920s–1950s and 1990s to present, whereas cold intervals occurred in the A.D. 1630s–1680s, 1790s–1800s, 1860s–1880s and 1950s–1980s, respectively. The low-frequency variation of the reconstruction agreed fairly well with tree-ring reconstructed temperature from nearby regions and with records of glacier fluctuations in the surrounding high mountains, suggesting that our reconstructed summer temperature was reliable, and could aid in the evaluation of regional climate variability.     

On the Use of the Jesuit Order Private Correspondence Records in Climate Reconstructions: A Case Study from Castille (Spain) for 1634–1648 A.D.

This work analyses the climatic information content of more than 1000 letters belonging to the private correspondence of the Jesuit order during the period 1634–1648. The information obtained mainly originates in Castille, and it was codified to obtain quantitative indices representative of the evolution of the thermal and rainfall anomalies. The results show that intense rainfall and cold air waves predominated during the study period, in accordance with other results on the climatic evolution of the Iberian Peninsula during the Little Ice Age.