Ozone exchange within and above an irrigated Californian orchard

In this study, the canopy effects on the vertical ozone exchange within and above Californian orchard are investigated. We examined the comprehensive dataset obtained from the Canopy Horizontal Array Turbulence Study (CHATS). CHATS typifies a rural central Californian site, with O3 mixing ratios of less than 60 ppb and moderate NOx mixing ratios. The CHATS campaign covered a complete irrigation cycle, with our analysis including periods before and after irrigation. Lower O3 mixing ratios were found following irrigation, together with increased wind speeds, decreased air temperatures and increased specific humidity. Friction velocity, sensible heat and gas fluxes above the canopy were estimated using variations on the flux-gradient method, including a method which accounts for the roughness sublayer (RSL). These methods were compared to fluxes derived from observed eddy diffusivities of heat and friction velocity. We found that the use of the RSL parameterization, which accounts for the canopy-induced turbulent mixing above the canopy, resulted in a stronger momentum, heat, and ozone exchange fluxes above this orchard, compared to the method which omits the RSL. This was quantified by the increased friction velocity, heat flux and ozone deposition flux of up to 12, 29, and 35% at 2.5 m above the canopy, respectively. Within the canopy, vertical fluxes, as derived from local gradients and eddy diffusivity of heat, were compared to fluxes calculated using the Lagrangian inverse theory. Both methods showed a presence of vertical flux divergence of friction velocity, heat and ozone, suggesting that turbulent mixing was inefficient in homogenizing the effects driven by local sources and sinks on vertical exchange of those quantities. This weak mixing within the canopy was also corroborated in the eddy diffusivities of friction velocity and heat, which were calculated directly from the observations. Finally, the influence of water stress on the O3 budget was examined by comparing the results prior and after the irrigation. Although the analysis is limited to the local conditions, our in situ measurements indicated differences in the O3 mixing ratio prior and after irrigation during CHATS. We attribute these O3 mixing ratio changes to enhanced biological emission of volatile organic compounds (VOCs), driven by water stress

Estimating ET using scintillometers and satellites in an irrigated vineyard in the Costa De Hermosillo, Sonora, Mexico

Observation techniques for surface energy balancecomponents on kilometer scale. Several methods have been proposed to estimate ET overlarge areas which combine Earth Observation Satellite datawith standard climate data. Here we use the Makkinkapproach where incoming solar radiation is obtained bycalculating exoatmospheric incoming solar radiation, usingvisible data from GOES West to estimate cloudiness and16-day composite MODIS Enhanced Vegetation Index data toestimate fractional vegetation cover. This methodology can beused operationally at a spatial resolution of 1 km2 butvalidation data are required at a similar spatial scale. LargeAperture Scintillometers transmit and receive near infraredradiation over distances of several kilometers and providemeasurements of the structure parameter for the refractiveindex of air which is related by Monin-Obukhov SimilarityTheory to the surface sensible heat flux (H), which requiresmeasurements of air temperature, pressure and wind speed.ET can then be obtained indirectly as the residual of theenergy balance, ET = Rn – G – H so that we need estimates ofNet Radiation (Rn) and Soil Heat Flux (G) as well. Ascintillometer (Scintec BLS-450) was installed over anirrigated vineyard with area of 72 hectares (1200m x 600m) inJune 6th 2009. Net Radiation was measured in the field andsoil heat flux was estimated using G = A * Rn, where theparameter A was obtained from 8-day composite MODIS LandSurface Temperature data. Comparison of ET derived fromsatellite and scintillometer for June 2009 showed considerablescatter with r2 = 0.81 and ETSAT = 1.12 * ETBLS. Thisapparent overestimation from the satellite-based ET is similarto that found in previous work. However, in these initialcalculations it was assumed that unstable conditions wouldprevail during the daytime but it appears that stableconditions often occur in the late afternoon. Secondly, theestimation of G needs to be carefully revised since this canhave a large effect on ET. These factors are being included inthe analysis of data over an entire growing season to assessthe seasonal behavior of the model

Unemployment Convergence in Central and Eastern European Countries: Driving Forces and Cluster Behavior

Employing a nonlinear logistic smooth transition autoregression system and comovement analysis, we find that the German business cycle has acted as a common driver affecting the cyclical behavior of unemployment rates in Central and Eastern European countries. In addition, we identify two convergence clubs in unemployment dynamics. The first comprises the Baltic States, Hungary, and Poland, and the second group of countries is composed of the Czech Republic and Slovakia. Interestingly, this classification matches the labor market policies and institutional divergences observed among these countries

Scintillometry in urban and complex environments: a review

Knowledge of turbulent exchange in complex environments is relevant to a wide range of hydro-meteorological applications. Observations are required to improve understanding and inform model parameterisations but the very nature of complex environments presents challenges for measurements. Scintillometry offers several advantages as a technique for providing spatially-integrated turbulence data (structure parameters and fluxes), particularly in areas that would be impracticable to monitor using eddy covariance, such as across a valley, above a city or over heterogeneous landscapes. Despite much of scintillometry theory assuming flat, homogeneous surfaces and ideal conditions, over the last 20 years scintillometers have been deployed in increasingly complex locations, including urban and mountainous areas. This review draws together fundamental and applied research in complex environments, to assess what has been learnt, summarise the state-of-the-art and identify key areas for future research. Particular attention is given to evidence, or relative lack thereof, of the impact of complex environments on scintillometer data. Practical and theoretical considerations to account for the effects of complexity are discussed, with the aim of developing measurement capability towards more reliable and accurate observations in future. The usefulness of structure parameter measurements (in addition to fluxes, which must be derived using similarity theory) should not be overlooked, particularly when comparing or combining scintillometry with other measurement techniques and model simulations

Firm heterogeneity and wages under different bargaining regimes : does a centralised union care for low-productivity firms?

This paper studies the relationship between wages and the degree of firm heterogeneity in a given industry under different wage setting structures. To derive testable hypotheses, we set up a theoretical model that analyses the sensitivity of wages to the variability in productivity conditions in a unionsised oligopoly framework. The model distinguishes centralised and decentralised wage determination. The theoretical results predict wages to be negatively associated with the degree of firm heterogeneity under centralised wage-setting, as unions internalise negative externalities of a wage increase for low-productivity firms. We test this prediction using a linked employeremployee panel data set from the German mining and manufacturing sector. Consistent with our hypotheses, the empirical results suggest that under industry-level bargaining workers in more heterogeneous sectors receive lower wages than workers in more homogeneous sectors. In contrast, the degree of firm heterogeneity is found to have no negative impact on wages in uncovered firms and under firm-level contracts