Impact of deep convection in the tropical tropopause layer in West Africa: in-situ observations and mesoscale modelling
Kathy S. Law
Guido Di Donfrancesco
- We present the analysis of the impact of convection on the composition of the tropical tropopause layer region (TTL) in West-Africa during the AMMA-SCOUT campaign. Geophysica M55 aircraft observations of water vapor, ozone, aerosol and CO2 during August 2006 show perturbed values at altitudes ranging from 14 km to 17 km (above the main convective outflow) and satellite data indicates that air detrainment is likely to have originated from convective cloud east of the flights. Simulations of the BOLAM mesoscale model, nudged with infrared radiance temperatures, are used to estimate the convective impact in the upper troposphere and to assess the fraction of air processed by convection. The analysis shows that BOLAM correctly reproduces the location and the vertical structure of convective outflow. Model-aided analysis indicates that convection can influence the composition of the upper troposphere above the level of main outflow for an event of deep convection close to the observation site. Model analysis also shows that deep convection occurring in the entire Sahelian transect (up to 2000 km E of the measurement area) has a non negligible role in determining TTL composition.
Soil moisture initialization effects in the Indian monsoon system
- Towards the goal to understand the role of land-surface processes over the Indian sub-continent, a series of soil-moisture sensitivity simulations have been performed using a non-hydrostatic regional climate model COSMO-CLM. The experiments were driven by the lateral boundary conditions provided by the ERA-Interim (ECMWF) reanalysis. The simulation results show that the pre-monsoonal soil moisture has a significant influence on the monsoonal precipitation. Both, positive and negative soil-moisture precipitation (S-P) feedback processes are of importance. The negative S-P feedback process is especially influential in the western and the northern parts of India.
Regional climate projections in two alpine river basins: Upper Danube and Upper Brahmaputra
- Projections from coarse-grid global circulation models are not suitable for regional estimates of water balance or trends of extreme precipitation and temperature, especially not in complex terrain. Thus, downscaling of global to regionally resolved projections is necessary to provide input to integrated water resources management approaches for river basins like the Upper Danube River Basin (UDRB) and the Upper Brahmaputra River Basin (UBRB).
This paper discusses the application of the regional climate model COSMO-CLM as a dynamical downscaling tool. To provide accurate data the COSMO-CLM model output was post-processed by statistical means. This downscaling chain performs well in the baseline period 1971 to 2000. However, COSMO-CLM performs better in the UDRB than in the UBRB because of a longer application experience and a less complex climate in Europe.
Different climate change scenarios were downscaled for the time period 1960–2100. The projections show an increase of temperature in both basins and for all seasons. The values are generally higher in the UBRB with the highest values occurring in the region of the Tibetan Plateau. Annual precipitation shows no substantial change. However, seasonal amounts show clear trends, for instance an increasing amount of spring precipitation in the UDRB. Again, the largest trends for different precipitation statistics are projected in the region of the Tibetan Plateau. Here, the projections show up to 50% longer dry periods in the months June to September with a simultaneous increase of about 10% for the maximum amount of precipitation on five consecutive days. For the Assam region in India, the projections also show an increase of 25% in the number of consecutive dry days during the monsoon season leading to prolonged monsoon breaks.
Interactive comment on "An open marine record of the Toarcian oceanic anoxic event" by D. R. Gröcke et al.
Bas van de Schootbrugge
A modification of the mixed form of Richards equation and its application in vertically inhomogeneous soils
- Recently, new soil data maps were developed, which include vertical soil properties like soil type. Implementing those into a multilayer Soil-Vegetation-Atmosphere-Transfer (SVAT) scheme, discontinuities in the water content occur at the interface between dissimilar soils. Therefore, care must be taken in solving the Richards equation for calculating vertical soil water fluxes. We solve a modified form of the mixed (soil water and soil matric potential based) Richards equation by subtracting the equilibrium state of soil matrix potential ψE from the hydraulic potential ψh. The sensitivity of the modified equation is tested under idealized conditions. The paper will show that the modified equation can handle with discontinuities in soil water content at the interface of layered soils.
Jahresbericht 2010 Geo-Agentur
The radiation budget in a regional climate model
- The aim of this study is a better understanding of radiation processes in regional climate models (RCMs) in order to quantify their impact and to reduce possible errors. A first important task in finding an answer to this question was to examine the accuracy of the components of the radiation budget in regional climate simulations. To this end, the simulated radiation budgets of two regional climate simulations for Europe were compared with a satellite-based reference. In the simulations with the RCM COSMO-CLM there were some serious under- and overestimations of short- and long-wave net radiation in Europe. However, taking into account the differences in the reference datasets, the results of the COSMO-CLM were quite satisfactory.
Using statistical methods, the influence of potential sources of uncertainties was estimated. Uncertainties in the cloud cover and surface albedo had a significant impact on uncertainties in short-wave net radiation, the explained variance of uncertainties in cloud cover was two to three times higher than that of uncertainties in surface albedo. Uncertainties in the cloud cover resulted in significant errors in the net long-wave radiation. However, the influence of uncertainties in soil temperature on errors in the long-wave radiation budget was low or even negligible. These results were confirmed in a comparison with simulations of the REMO and ALADIN regional climate models. It is reasonable to expect that a better parameterization of relatively simple parameters such as cloud cover and surface albedo is a means of significantly improving the simulation of radiation budget components in the COSMO-CLM.
An important question for the application of RCMs is to examine whether the results of radiation uncertainties and their impact factors are comparable if the model is applied in a region that is not the one for which it was originally created. Comparisons of the simulated radiation budgets of different RCMs for West Africa showed that problems in the simulation of short- and long-wave radiation fluxes were a widespread problem. Most of the tested models showed some considerable under- or overestimation of the short- and long-wave radiation fluxes.
Similar to Europe uncertainties in cloud cover were also in the simulations for Africa a significant factor affecting uncertainties in the simulated radiation fluxes. However, for the African simulations uncertainties in the parameterization of surface albedo were much more important than in Europe. On average, overland uncertainties in the cloud cover and surface albedo were of similar importance. Uncertainties in soil temperature simulations were of higher importance in Africa, and reached overland similar values of the mean explained variance (R2 ≈ 0.2) such as uncertainties in the cloud cover. This indicates a geographical dependence of the model error. This study confirmed the assumption that an improved parameterization of relatively simple parameters such as the surface albedo in RCMs leads to a significant improvement in the modeled radiation budget, particularly in Africa.
The influence of errors in the simulated radiation budget components on the simulation of climate processes, such as the West-African monsoon (WAM), was investigated in a next step. The evaluation of ERA-Interim and ECHAM5 driven COSMO-CLM simulations for Africa showed that the main features of the WAM were well reproduced by the model, but there were only slight improvements compared to the driving data. The index of convective activity in the model simulations was much too high and precipitation was underestimated in large parts of tropical Africa. The partly considerable differences between the ERA-Interim and ECHAM5 driven simulations demonstrated the sensitivity of the RCM to the boundary conditions and in particular to the sea surface temperature. An excessive northwards shift of the monsoon in the model was influenced by the land-sea temperature gradient and the strength of the Saharan heat low. Consequently, a part of the error was due to the driving data and the model itself produced another part.
By modifying the parameterization of the bare soil albedo the errors in the radiation budget and 2 m temperature in the Sahara region were significantly reduced. Similarly, the overesti-mation of precipitation and convection has been reduced in the Sahel. The effect of this modifi-cation on the examined WAM area was low. This confirmed that especially in desert regions, errors in the surface albedo were a driving factor for errors in the radiation budget. However, there are other important factors not yet sufficiently understood that have a strong influence on the quality of the simulation of the WAM.
The analysis of the actual state, the quantification of error sources and the highlighting of connections made it possible to find means to reduce uncertainties in the simulated radiation in RCMs and to have a better understanding of radiation processes. However, the magnitude of the errors found, the number of possible influencing factors, and the complexity of interactions, indicate that there is still a need for further research in this area.
Occurrence and sources of 2,4,7,9-tetramethyl-5-decyne-4,7-diol (TMDD) in the aquatic environment
Arlen Guedez Orozco
- The aim of the present study was to identify the sources of 2,4,7,9-tetramethyl-5-decyne-4,7-
diol (TMDD) into the aquatic environment and to investigate its occurrence in rivers and
wastewater treatment plants (WWTPs). Therefore, TMDD was analyzed in 441 wastewater
samples from influents and effluents of 27 municipal WWTPs, in 6 sludge samples, in 52
wastewater samples from 3 sewage systems of municipal WWTPs, in 489 surface samples
from 24 rivers, in 9 wastewater samples of 3 paper-recycling industries and in 65 groundwater
samples. TMDD was also analyzed in household paper products, in 23 samples of toilet
papers, in 5 types of paper towels and in 12 types of paper tissues. The samples were collected
between 2007 and 2011. The water samples were extracted with solid phase extraction (SPE)
and the household paper samples with Soxhlet extraction. Gas chromatography-mass
spectrometry (GC-MS) was used for quantification purposes.
Between November 2007 and January 2008, TMDD was detected in the river Rhine at Worms
with permanent high concentrations (up to 1330 ng/L). The results showed that TMDD is
uniformly distributed across the river at Worms. An increase of the mean TMDD
concentration from approximately 500 ng/L to 1000 ng/L was registered in January 2008. Due
to the minor fluctuations of the TMDD concentration during the sampling period it is
expected that the input of TMDD into the river is continuous. Therefore, TMDD might rather
originate from effluents of municipal WWTPs than from temporal sources. The mean TMDD
load based on the analysis of 147 water samples collected in the River Rhine was 62.8 kg/d
which is equivalent to 23 t/a suggesting that TMDD must be used and/or produced in high
quantities in order to be found in those high concentrations. To determine if TMDD is
discharged by effluents of municipal WWTPs into the rivers, 24 hours influent and effluent
samples of four municipal WWTPs in the Frankfurt/Rhine-Main metropolitan region were
collected during November 2008 and February 2010 and analyzed for TMDD. The TMDD
influent concentrations varied between 134 ng/L and 5846 ng/L and the effluent
concentrations between <LOQ (limit of quantitation) and 3539 ng/L. The TMDD elimination
rates in the four WWTPs varied between 33% and 68%. The results showed that effluents of
municipal WWTPs are an important source of TMDD in the aquatic environment because
TMDD is not completely removed from the sewage during the wastewater treatment. Weekly
and daily variations of the TMDD concentration in the influents of two municipal WWTPs
indicated that both private households and indirect industrial dischargers contribute to the
introduction of TMDD into the municipal sewage systems. A more detailed study of the
TMDD elimination rate in the different wastewater treatment stages was carried out in the
WWTP Niederrad/Griesheim in Frankfurt am Main. The results showed that the removal of
TMDD is mainly carried out during the aerobic biological treatments, where the elimination
rate was 46%. In contrast, during the anoxic treatment the removal efficiency was only 1.4%
and during the mechanical treatment the elimination rate was 19%.
To determine the sources of TMDD in the sewage, household paper products (paper tissues,
toilet papers and paper towels) were analyzed for TMDD using Soxhlet extraction. TMDD
was detected in 83% of the samples (n=40). The highest mean TMDD concentrations were
found in recycled toilet paper (0.20 μg/g) and in paper towels (0.11 μg/g). In paper tissues and
non-recycled toilet paper the mean TMDD concentrations were lower 0.080 μg/g and
0.025 μg/g respectively. According to these results the high TMDD influent concentrations
found previously in municipal WWTPs (mean 1.20 μg/L) cannot be explained due to
migration of TMDD from the household paper products into the sewage. Thus indirect
industrial dischargers are the cause of the high influent TMDD concentrations. Effluents of
municipal WWTPs with different indirect industrial dischargers (textile-, metal processing-,
food processing-, electroplating-, paper-recycling- and printing ink factories) were analyzed.
The highest mean TMDD concentrations were found in the effluents of municipal WWTPs
that have paper-recycling (71.3 μg/L) and printing ink factories (138 μg/L) as indirect
industrial dischargers. These results were confirmed by analyzing process wastewater of three
paper-recycling factories located in Germany. High TMDD concentrations were detected and
fluctuated between 1.83 μg/L and 113 μg/L. TMDD was also analyzed in the wastewater of a
non-recycling-paper factory but its concentration was much lower (0.066 μg/L) indicating that
TMDD is introduced into the processing water during the papermaking process due to the use
of waste paper. Analyses of wastewater samples from different parts of the sewage pipes of a
municipal WWTP in Hesse, which receives the wastewater from a printing ink factory, were
carried out. The TMDD concentration in the wastewater sample from the sewage pipe of the
printing ink factory was much higher (3,300 μg/L) than the TMDD concentration detected in
the other wastewater samples from the sewage system (0.030 μg/L – 0.89 g/L). These results
confirm the printing ink production as one of the principal sources of TMDD in the sewage.
Analysis of surface water samples of the River Modau downstream from the effluent of the
WWTP Nieder-Ramstadt showed TMDD concentrations of up to 28.0 μg/L. These high
TMDD concentrations might be caused by the indirect wastewater discharges of a paint
factory connected to the municipal sewage system. These results indicate that TMDD is
introduced into the municipal WWTPs principally by indirect industrial dischargers and they
are mainly paint and printing ink factories. The paper-recycling factories also represent an
important source of TMDD in municipal WWTPs but indirectly. According to statements
given by the representatives of two paper recycling factories neither TMDD or any other
TMDD containing product is used or added during the papermaking process. Therefore,
TMDD is washed out from the printing inks of the coloured waste paper and concentrated in
the process wastewater in the closed water circuits of paper-recycling factories reaching rivers
and municipal WWTPs.
The occurrence and distribution of TMDD in surface waters in Germany was also studied.
The results showed that TMDD is widely distributed across different rivers systems in the
federal states of Hesse, North-Rhine-Westphalia, Bavaria, Baden-Wuerttemberg and
Rhineland-Palatinate. In Hesse, TMDD was detected in the some of main rivers with mean
concentrations of 812 ng/L (Schwarzbach, Hessian Ried), 374 ng/L (Kinzig), 393 ng/L (Main,
at Frankfurt), 539 ng/L (Werra), 326 ng/L (Fulda), 151 ng/L (Emsbach) and 161 ng/L
(Nidda). In small rivers (creeks) the mean TMDD concentrations varied between <LOQ
(Diemel, Urselbach) and 1890 ng/L (Darmbach). The results showed that the TMDD
concentrations in creeks are highly influenced by both effluents of WWTPs and by the
distance between the sampling point and the nearest WWTP. Surface samples from sampling
locations downstream from WWTPs dischargers showed higher TMDD concentrations (mean
518 ng/L) than sampling locations upstream from WWTPs dischargers (mean 35.1 ng/L).
The behavior of TMDD during bank filtration was investigated at two locations, at a water
utility company at the Lower River Rhine (urban area) and at the Oderbruch polder (rural
area). The results indicated that TMDD is removed from the surface water by bank filtration
at both sampling locations. The removal process is probably carried out in the first meters of
the aquifer (hyporheic zone) by biodegradation processes, since TMDD does not tend to be
absorbed by sediments and it was not found in the groundwater of monitoring wells. In
groundwater samples from the Hessian Ried (n=23) TMDD was found only in five samples
and the highest TMDD concentration was 135 ng/L. According to these results, TMDD does
not represent a concern for drinking water in Germany, since it does not reach the
groundwater with high concentrations and it has a low toxicity potential.
The input of TMDD into the North Sea was estimated to be 60.7 t/a by considering the mean
transported loads of TMDD by the River Rhine at Wesel (58.3 t/a) and Meuse in the
Netherlands (2.40 t/a). The estimated discharge of TMDD by German municipal WWTPs
(8.19 t/a) and paper-recycling factories (9.24 t/a) into rivers seems to be too low considering
that the mean TMDD load in the River Rhine downstream from Wesel is 58.3 t/a. However,
due to the high density of population and industries at the Lower Rhine it is expected that
more relevant sources of TMDD are located along the Rhine River increasing the transported
According to the results of this PhD project TMDD is a non-ionic surfactant contained in
products, which are applied on surfaces (printing inks and paints) and has the potential to
reach the aquatic environment. Therefore, TMDD should fulfill the requirement of a
biodegradability of 80% established by the “Law on the Environmental Impact of Detergents
and Cleaning Products” in Germany. However, due to the partial elimination rates of TMDD
obtained in municipal WWTPs (between 33% and 68%) and to the absence of information
about the execution of the biodegradation test on TMDD, it is unknown if TMDD is in
accordance with this law. Otherwise, its use as surfactant in such products is questionable.
Vom Treibhausklima der Kreidezeit zum heutigen Eishausklima : auf Spurensuche in Mikrofossilien vom Meeresboden
- Wenn Klimaforscher wissen wollen, was die Zukunft
bringt, schauen sie gern in die Vergangenheit. Während
der Kreidezeit herrschte auf der Erde ein Treibhausklima
mit atmosphärischen CO2-Gehalten, die weitaus
höher waren als heute. Welche Konsequenzen das für
die Meeresströmungen und die marinen Ökosysteme
hatte, können Geowissenschaftler heute nicht mehr direkt
messen. Bei der Spurensuche helfen ihnen die
Fossilien mikroskopisch kleiner Einzeller, deren wunderschöne
Kalkschalen als Klimagedächtnis dienen.
An object-based classification approach for mapping "migrant housing" in the mega-urban area of the Pearl River Delta (China)
- Urban areas develop on formal and informal levels. Informal development is often highly dynamic, leading to a lag of spatial information about urban structure types. In this work, an object-based remote sensing approach will be presented to map the migrant housing urban structure type in the Pearl River Delta, China. SPOT5 data were utilized for the classification (auxiliary data, particularly up-to-date cadastral data, were not available). A hierarchically structured classification process was used to create (spectral) independence from single satellite scenes and to arrive at a transferrable classification process. Using the presented classification approach, an overall classification accuracy of migrant housing of 68.0% is attained.