Water management in PEMFC: 1-D model simulations

2016 ◽  
Vol 28 (2) ◽  
pp. 81-87 ◽  
Author(s):  
D.S. Falcão ◽  
C. Pinho ◽  
A.M.F.R. Pinto
Keyword(s):  
Water Management ◽  
Model Simulations ◽  
D Model

scholarly journals The roles of vertical advection and eddy diffusion in the equatorial mesospheric semi-annual oscillation (MSAO)

2013 ◽  
Vol 13 (15) ◽  
pp. 7813-7824 ◽  
Author(s):  
R. L. Gattinger ◽  
E. Kyrölä ◽  
C. D. Boone ◽  
W. F. J. Evans ◽  
K. A. Walker ◽  
...  
Keyword(s):  
Driving Forces ◽  
Eddy Diffusion ◽  
Equatorial Region ◽  
Local Times ◽  
Model Simulations ◽  
Vertical Advection ◽  
Diffusion Rates ◽  
D Model ◽  
Vertical Eddy

Abstract. Observations of the mesospheric semi-annual oscillation (MSAO) in the equatorial region have been reported dating back several decades. Seasonal variations in both species densities and airglow emissions are well documented. The extensive observations available offer an excellent case study for comparison with model simulations. A broad range of MSAO measurements is summarised with emphasis on the 80–100 km region. The objective here is not to address directly the complicated driving forces of the MSAO, but rather to employ a combination of observations and model simulations to estimate the limits of some of the underlying dynamical processes. Photochemical model simulations are included for near-equinox and near-solstice conditions, the two times with notable differences in the observed MSAO parameters. Diurnal tides are incorporated in the model to facilitate comparisons of observations made at different local times. The roles of water vapour as the "driver" species and ozone as the "response" species are examined to test for consistency between the model results and observations. The simulations suggest the interactions between vertical eddy diffusion and background vertical advection play a significant role in the MSAO phenomenon. Further, the simulations imply there are rigid limits on vertical advection rates and eddy diffusion rates. For August at the Equator, 90 km altitude, the derived eddy diffusion rate is approximately 1 × 106 cm2 s−1 and the vertical advection is upwards at 0.8 cm s−1. For April the corresponding values are 4 × 105 cm2 s−1 and 0.1 cm s−1. These results from the current 1-D model simulations will need to be verified by a full 3-D simulation. Exactly how vertical advection and eddy diffusion are related to gravity wave momentum as discussed by Dunkerton (1982) three decades ago remains to be addressed.

scholarly journals Lifetime and production rate of NOx in the upper stratosphere and lower mesosphere in the polar spring/summer after the solar proton event in October–November 2003

2012 ◽  
Vol 12 (7) ◽  
pp. 17703-17721
Author(s):  
F. Friederich ◽  
T. von Clarmann ◽  
B. Funke ◽  
H. Nieder ◽  
J. Orphal ◽  
...  
Keyword(s):  
Production Rate ◽  
Polar Region ◽  
Solar Proton ◽  
Ion Pair ◽  
Solar Proton Event ◽  
Proton Event ◽  
Production Rates ◽  
Model Simulations ◽  
D Model ◽  
Ionization Rates

Abstract. We present altitude dependent lifetimes of NOx, determined with MIPAS/ENVISAT, for the southern polar region after the solar proton event in October–November 2003. Varying in latitude and decreasing in altitude they range from about two days at 64 km to about 20 days at 44 km. The lifetimes are controlled by transport, mixing and photolysis. We infer dynamical lifetimes by comparison of the observed decay to photolytical lifetimes calculated with the SLIMCAT 3-D Model. Photochemical loss contributes to the observed NOx depletion by 10% at 44 km, increasing with altitude to 35% at 62 km at a latitude of –63° S. At higher latitudes, the contribution of photochemical loss can be even more important. In addition, we show the correlation of modeled ionization rates and observed NOx densities under consideration of the determined lifetimes of NOx, and calculate altitude dependent effective production rates of NOx due to ionization. For that we compare ionization rates of the AIMOS data base with the MIPAS measurements for the whole Austral polar summer 2003/04. We derive effective NOx-production rates to be applied to the AIMOS ionization rates which range from about 0.2 NOx-molecules per ion pair at 44 km to 0.9 NOx-molecules per ion pair at 54 km at a latitude of –63° S. At –73° S, the NOx-production rate ranges from about 0.2 NOx-molecules per ion pair at 44 km to 1.0 NOx-molecules per ion pair at 60 km. These effective production rates are considerably lower than predicted by box model simulations which could hint at an overestimation of the modeled ionization rates.

scholarly journals Albedo and heat transport in 3-D model simulations of the early Archean climate

2013 ◽  
Vol 9 (4) ◽  
pp. 1841-1862 ◽  
Author(s):  
H. Kienert ◽  
G. Feulner ◽  
V. Petoukhov
Keyword(s):  
Heat Transport ◽  
General Circulation ◽  
Climate Model ◽  
Stable State ◽  
Circulation Model ◽  
Ocean Surface ◽  
Meridional Heat Transport ◽  
Model Simulations ◽  
D Model ◽  
Archean Climate

Abstract. At the beginning of the Archean eon (ca. 3.8 billion years ago), the Earth's climate state was significantly different from today due to the lower solar luminosity, smaller continental fraction, higher rotation rate and, presumably, significantly larger greenhouse gas concentrations. All these aspects play a role in solutions to the "faint young Sun paradox" which must explain why the ocean surface was not fully frozen at that time. Here, we present 3-D model simulations of climate states that are consistent with early Archean boundary conditions and have different CO2 concentrations, aiming at an understanding of the fundamental characteristics of the early Archean climate system. In order to do so, we have appropriately modified an intermediate complexity climate model that couples a statistical-dynamical atmosphere model (involving parameterizations of the dynamics) to an ocean general circulation model and a thermodynamic-dynamic sea-ice model. We focus on three states: one of them is ice-free, one has the same mean surface air temperature of 288 K as today's Earth and the third one is the coldest stable state in which there is still an area with liquid surface water (i.e. the critical state at the transition to a "snowball Earth"). We find a reduction in meridional heat transport compared to today, which leads to a steeper latitudinal temperature profile and has atmospheric as well as oceanic contributions. Ocean surface velocities are largely zonal, and the strength of the atmospheric meridional circulation is significantly reduced in all three states. These aspects contribute to the observed relation between global mean temperature and albedo, which we suggest as a parameterization of the ice-albedo feedback for 1-D model simulations of the early Archean and thus the faint young Sun problem.

scholarly journals Spatial-Temporal Evaluation of Rain-Fauge Network Based on Entropy Theory

10.29007/1kc9 ◽  
2018 ◽  
Author(s):  
Wenqi Wang ◽  
Dong Wang ◽  
Vijay P. Singh ◽  
Yuankun Wang
Keyword(s):  
Water Management ◽  
Information Theory ◽  
Network Design ◽  
Spatial Model ◽  
Rain Gauge ◽  
Entropy Theory ◽  
Precipitation Data ◽  
D Model ◽  
Rain Gauge Network

Ground-based rain-gauge stations are the most direct sources of precipitation data. The evaluation of rain-gauge network is essential and important for water management. One of the most popular methods for design of hydrometric network including rain- gauge network is information theory. Entropy concepts from information theory has been widely adopted and applied in rain-gauge network design. In this paper, spatial- temporal evaluation of rain-gauge network located in Shanghai, China will be performed based on entropy theory. The transinformation-distance (T-D) spatial model is applied under three different sampling frequencies. Weekly precipitation data fits the T-D model best. In addition, the representative network is evaluated to be suitable according to the result.

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