Response of flower and boll development to climatic factors in Egyptian cotton (Gossypium barbadense)

Fruiting of cotton plant is determined and influenced by cultivars, climatic conditions, management practices and pests. An understanding of the flowering and boll retention patterns of cotton cultivars can contribute to more efficient and economical crop management. The objective of this investigation was to study the effect of various climatic factors on flower and boll production, and also, the nature of its effects prevailing prior and subsequent to either flowering or boll setting on flower and boll production and retention in Egyptian cotton. This could be used in formulating advanced prediction of the effect of certain climatic conditions on the production of Egyptian cotton. Also, the study focused on four equal periods during the development of flower and bolls stage to study the response of these characters to climatic factors during these periods and to determine the most representative period corresponding to the overall crop pattern. Further, the study predicting effects of climatic factors during convenient intervals (in days) on cotton flower and boll production compared with daily observations to find the optimum interval. Evaporation, sunshine duration, humidity, surface soil temperature at 1800 h, and maximum air temperature, are the important climatic factors that significantly affects flower and boll production. Evaporation; minimum humidity and sunshine duration were the most effective climatic factors during preceding and succeeding periods on boll production and retention. There was a negative correlation between flower and boll production and either evaporation or sunshine duration, while that correlation with minimum humidity was positive. The fourth quarter period of the production stage was the most appropriate and usable time to collect data for determining efficient prediction equations for cotton production. Evaporation, humidity and temperature were the principal climatic factors that governed cotton flower and boll production during the fourth quarter. The five day interval was found to be adequately and sensibly related to yield parameters than other intervals and was closest to the daily observations. Evaporation was found to be the most important climatic variable affecting flower and boll production, followed by humidity. An accurate weather forecast 5–7 days in advance would provide an opportunity to avoid adverse effects of climatic factors on cotton production through utilizing proper cultural practices which would limit and control their negative effects.     

Estimating the Soil Moisture Profile by Assimilating Near-Surface Observations with the Ensemble Kalman Filter （EnKF）

The paper investigates the ability to retrieve the true soil moisture profile by assimilating near-surface soil moisture into a soil moisture model with an ensemble Kalman filter （EnKF） assimilation scheme, including the effect of ensemble size, update interval and nonlinearities in the profile retrieval, the required time for full retrieval of the soil moisture profiles, and the possible influence of the depth of the soil moisture observation. These questions are addressed by a desktop study using synthetic data. The ＂true＂ soil moisture profiles are generated from the soil moisture model under the boundary condition of 0.5 cm d^-1 evaporation. To test the assimilation schemes, the model is initialized with a poor initial guess of the soil moisture profile, and different ensemble sizes are tested showing that an ensemble of 40 members is enough to represent the covariance of the model forecasts. Also compared are the results with those from the direct insertion assimilation scheme, showing that the EnKF is superior to the direct insertion assimilation scheme, for hourly observations, with retrieval of the soil moisture profile being achieved in 16 h as compared to 12 days or more. For daily observations, the true soil moisture profile is achieved in about 15 days with the EnKF, but it is impossible to approximate the true moisture within 18 days by using direct insertion. It is also found that observation depth does not have a significant effect on profile retrieval time for the EnKF. The nonlinearities have some negative influence on the optimal estimates of soil moisture profile but not very seriously.     

Dynamical Feedback between Synoptic Eddy and Low-Frequency Flow as Simulated by BCC_CSM1.1(m)

Since the interaction between atmospheric synoptic eddy(SE)(2–8 days) activity and low-frequency(LF)(monthly)flow(referred to as SELF) plays an essential role in generating and maintaining dominant climate modes,an evaluation of the performance of BCC_CSM1.1(m) in simulating the SE feedback onto the LF flow is given in this paper.The model captures well the major spatial features of climatological eddy vorticity forcing,eddy-induced growth rate,and patterns of SELF feedback for the climate modes with large magnitudes in cold seasons and small magnitudes in warm seasons for both the Northern and Southern Hemisphere.As in observations,the eddy-induced growth rate and SELF feedback patterns in the model also show positive SE feedback.Overall,the relationships between SE and LF flow show that BCC_CSM1.1(m)satisfactorily captures the basic features of positive SE feedback,which demonstrates the simulation skill of the model for LF variability.Specifically,such an evaluation can help to find model biases of BCC_CSM1.1(m) in simulating SE feedback,which will provide a reference for the model's application.     

Seasonal and global NOx production by lightning estimated from the Optical Transient Detector (OTD)

The Optical Transient Detector (OTD) lightning data for the 12‐month period of 1996 are used to estimate the seasonal and global distributions of lightning‐produced NO _x . The relatively small viewing footprint and the low detection efficiency of the OTD sensor and other difficulties require extrapolations of the OTD data to the actual global flash distributions. Furthermore, available measurements for the ratios of intracloud (IC) to cloud‐to‐ground (CG) flashes have been used to partition lightning counts for IC versus CG flashes from the OTD observations. The resulting lightning distributions are then used to calculate the global and seasonal production of NO _x , assuming a NO production rate of 6.2×10²⁵ molecules for each CG flash and 8.7×10²⁴ molecules for each IC flash. Consequently, we find that CG flashes produce more NO _x than IC flashes despite fewer CG flashes by a factor of 3 or more. NO _x production by lightning varies seasonally in accordance with the global lightning distribution, with the maximum production occurring in the Northern Hemisphere in the local summer. The latitudinal distribution of NO _x production exhibits a strong seasonal variation outside the tropics with the production occurring mainly in the summer hemisphere, whereas in the tropics the production is high throughout the year. The annual contribution to NO _x production by lightning is higher in the Northern Hemisphere than that in the Southern Hemisphere.     

The pollen counts as bioindicator of meteorological trends and tool for assessing the status of endangered species: the case of Artemisia in Sierra Nevada (Spain)

This study sought to analyse the effects of climate change on Artemisia species growing in Sierra Nevada, a high mountain range in the south-east of the Iberian Peninsula, using pollen counts as a bioindicator. The study also examined the impact of Recovery Programmes implemented for the most endangered of these species. Analysis of historical Artemisia pollen-data series from 1992 to 2011 showed that flowering took place between late July and late September, but the trend towards higher summer temperatures detected over the series as a whole appeared to have delayed the start of flowering and brought forward the end of flowering, thus prompting a shortening of the season. A trend was also observed towards a delayed peak pollen period, together with a significant decline in the Annual Pollen Index, which was significantly influenced by rainfall over the months immediately prior to flowering. Recovery Programmes implemented for three species—Artemisia granatensis, A. alba subsp. nevadensis and A. umbelliformis—involved conservation measures including direct seeding and planting of seedlings. From the outset, these programmes led to a recovery of the Pollen Index, especially when using germinated seedlings, which adapted better than seeds to environmental conditions. In conclusion, pollen records proved to be a useful tool for assessing the status of endangered species.     

Current and perturbed climate as simulated by the second-generation Canadian Regional Climate Model (CRCM-II) over northwestern North America

An updated version of the Canadian Regional Climate Model (CRCM-II) has been used to perform time-slice simulations over northwestern North America, nested in the coupled Canadian General Circulation Model (CGCM2). Both driving and driven models are integrated in a scenario of transient greenhouse gases (GHG) and aerosols. The time slices span three decades that were chosen to correspond roughly to single, double and triple current GHG concentration levels. Several enhancements have been implemented in CRCM-II since the CRCM-I climate-change simulations reported upon earlier. The larger computational domain, extending further to the west, north and south, allows for a better spin-up of weather systems as they enter the regional domain. The increased length of the simulations, from 5 to 10 years, strengthens the statistical robustness of the results. The improvements to the physical parameterisation, notably the moist convection scheme and the diagnostic cloud formulation, cure the excessive cloud cover problem present in CRCM-I, reduce the warm surface bias and prevent the occurrence of grid-point precipitation storms that occurred with CRCM-I in summer. The dynamical ocean and sea-ice components of CGCM2 that is used to provide atmospheric lateral and surface boundary conditions to CRCM-II, as well as the use of transient rather than equilibrium conditions of GHG and the inclusion of direct aerosols forcing, in both CGCM2 and CRCM-II, increase the realism of the CRCM-II climate-change simulation.     

Global and Regional Impacts of Vegetation on the Hydrological Cycle and Energy Budget as Represented by the Community Atmosphere Model （CAM3）

The effects of vegetation and its seasonal variation on energy and the hydrological cycle were examined using a state-of-the-art Community Atmosphere Model （CAM3）. Three 15-year numerical experiments were completed： the first with realistic vegetation characteristics varying monthly （VEG run）, the second without vegetation over land （NOVEG run）, and the third with the vegetation characteristics held at their annual mean values （VEGMEAN run）. In these models, the hydrological cycle and land surface energy budget were widely affected by vegetation. Globaland annual-mean evapotranspiration significantly increased compared with the NOVEG by 11.8% in the VEG run run, while runoff decreased by 13.2% when the realistic vegetation is incorporated. Vegetation plays different roles in different regions. In tropical Asia, vegetation-induced cooling of the land surface plays a crucial role in decreasing tropical precipitation. In middle latitudes and the Amazon region, however, the vegetation-induced increase of evapotranspiration plays a more important role in increasing precipitation. The seasonal variation of vegetation also shows clear influences on the hydrological cycle and energy budget. In the boreal mid-high latitudes where vegetation shows a strong seasonal cycle, evapotranspiration and precipitation are higher in the summer in the VEG run than in the VEGMEAN run.     

Long-term investigations on the water budget quantities predicted by the hydro-thermodynamic soil vegetation scheme (HTSVS) – Part II: Evaluation, sensitivity, and uncertainty

Summary ¶Various water budget elements (water supply to the atmosphere, ground water recharge, change in storage) are predicted by HTSVS for a period of 2050 days. The predicted water budget elements are evaluated by routine lysimeter data. The results show that land surface models need parameterizations for soil frost, snow effects and water uptake to catch the broad cycle of soil water budget elements. In principle, HTSVS is able to simulate the general characteristics of the seasonal changes in these water budget elements and their long-term accumulated sums. Compared to lysimeter data, there is a discrepancy in the predicted water supply to the atmosphere for summer and winter which may be attributed to the hardly observed plant physiological parameters like root depth, LAI, shielding factor, etc., the lack of measured downward long-wave radiation, and some simplifications made in the parameterizations of soil frost and snow effects. The fact that high resolution data for the evaluation of model results are missing and evaluation is made on the basis of the data from routine stations of a network is typical for the results of long-term studies on climate. Taking into account the coarse resolution of climate models, the coarse vertical resolution that is used in their LSMs, and the lack of suitable parameters needed, it seems that discrepancies in the order of magnitude found in this study are a general uncertainty in the results of land surface modeling on typical spatial and temporal scales of the climate system.Received October 8, 2001; revised February 15, 2002; accepted September 20, 2002 Published online: April 10, 2003     

The CO2-induced thickening/thinning of the Greenland and Antarctic ice sheets as simulated by a GCM (CCMI) and an ice-sheet model

Scaling analysis shows that the mean thickness of an ice sheet depends on the product of two poorly known quantities, the ice viscosity and the net snow accumulation rate. We adjust the viscosity of an ice sheet in order to get a consistent value of this product for the present-day ice sheet volume and area given the net snow accumulation rate calculated by an atmospheric general circulation model (GCM). We then hold this artificial rheology constant in further numerical experiments. We hope that in doing so we can partially compensate for systematic GCM errors in simulating the snow accumulation rate, and, therefore, thickening/thinning of ice sheets will depend mostly on the tendency in the net accumulation change rather than on its absolute value. Using this approach, the response of the Greenland and Antarctic ice sheets to doubling CO₂ concentration is simulated and the horizontal distribution of possible thickening/thinning of polar ice obtained. We find that, initially, the region of thickening ice is close to the area of increased snowfall rate, but later it significantly changes under the influence of internal ice flow dynamics. The sea-level changes predicted by our experiments agree with some empirical estimates. The sensitivity experiment with assigned basal sliding does not show significant changes in the large-scale ice topography, meaning, for example, that there is no indication of a possible disintegration of the West Antarctic ice sheet. At the same time, the regional thickening/thinning of ice (and consequently the sea-level change) depends strongly on processes at the ice sheet bottom.     

Near future (2016-40) summer precipitation changes over China as projected by a regional climate model (RCM) under the RCP8.5 emissions scenario: Comparison between RCM downscaling and the driving GCM

Multi-decadal high resolution simulations over the CORDEX East Asia domain were performed with the regional climate model RegCM3 nested within the Flexible Global Ocean-Atmosphere-Land System model, Grid-point Version 2 (FGOALS-g2). Two sets of simulations were conducted at the resolution of 50 km, one for present day (1980–2005) and another for near-future climate (2015–40) under the Representative Concentration Pathways 8.5 (RCP8.5) scenario. Results show that RegCM3 adds value with respect to FGOALS-g2 in simulating the spatial patterns of summer total and extreme precipitation over China for present day climate. The major deficiency is that RegCM3 underestimates both total and extreme precipitation over the Yangtze River valley. The potential changes in total and extreme precipitation over China in summer under the RCP8.5 scenario were analyzed. Both RegCM3 and FGOALS-g2 results show that total and extreme precipitation tend to increase over northeastern China and the Tibetan Plateau, but tend to decrease over southeastern China. In both RegCM3 and FGOALS-g2, the change in extreme precipitation is weaker than that for total precipitation. RegCM3 projects much stronger amplitude of total and extreme precipitation changes and provides more regional-scale features than FGOALS-g2. A large uncertainty is found over the Yangtze River valley, where RegCM3 and FGOALS-g2 project opposite signs in terms of precipitation changes. The projected change of vertically integrated water vapor flux convergence generally follows the changes in total and extreme precipitation in both RegCM3 and FGOALS-g2, while the amplitude of change is stronger in RegCM3. Results suggest that the spatial pattern of projected precipitation changes may be more affected by the changes in water vapor flux convergence, rather than moisture content itself.