Publications by Jorge Garcia-Franco

Revisiting gradient wind balance in tropical cyclones using dropsonde observations

Quarterly Journal of the Royal Meteorological Society Wiley (2020) qj.3947

JL García‐Franco, J Schwendike

The American monsoon system in HadGEM3 and UKESM1

Weather and Climate Dynamics Copernicus Publications 1 (2020) 349-371

JL García-Franco, S Osprey, LJ Gray

The simulated climate of the American monsoon system (AMS) in the UK models HadGEM3 GC3.1 (GC3) and the Earth system model UKESM1 is assessed and compared to observations and reanalysis. We evaluate the pre-industrial control, AMIP and historical experiments of UKESM1 and two configurations of GC3: a low (1.875∘×1.25∘) and a medium (0.83∘×0.56∘) resolution. The simulations show a good representation of the seasonal cycle of temperature in monsoon regions, although the historical experiments overestimate the observed summer temperature in the Amazon, Mexico and Central America by more than 1.5 K. The seasonal cycle of rainfall and general characteristics of the North American monsoon of all the simulations agree well with observations and reanalysis, showing a notable improvement from previous versions of the HadGEM model. The models reasonably simulate the bimodal regime of precipitation in southern Mexico, Central America and the Caribbean known as the midsummer drought, although with a stronger-than-observed difference between the two peaks of precipitation and the dry period. Austral summer biases in the modelled Atlantic Intertropical Convergence Zone (ITCZ), cloud cover and regional temperature patterns are significant and influence the simulated regional rainfall in the South American monsoon. These biases lead to an overestimation of precipitation in southeastern Brazil and an underestimation of precipitation in the Amazon. The precipitation biases over the Amazon and southeastern Brazil are greatly reduced in the AMIP simulations, highlighting that the Atlantic sea surface temperatures are key for representing precipitation in the South American monsoon. El Niño–Southern Oscillation (ENSO) teleconnections, of precipitation and temperature, to the AMS are reasonably simulated by all the experiments. The precipitation responses to the positive and negative phase of ENSO in subtropical America are linear in both pre-industrial and historical experiments. Overall, the biases in UKESM1 and the low-resolution configuration of GC3 are very similar for precipitation, ITCZ and Walker circulation; i.e. the inclusion of Earth system processes appears to make no significant difference for the representation of the AMS rainfall. In contrast, the medium-resolution HadGEM3 N216 simulation outperforms the low-resolution simulations due to improved SSTs and circulation.

Air quality in Mexico city during the fuel shortage of January 2019


JL Garcia-Franco

© 2019 Elsevier Ltd The closure of pipelines to tackle fuel-theft in central Mexico caused an unexpected fuel shortage that disrupted transport systems in Mexico City in January of 2019. Fuel sales in the Metropolitan Area and CO emissions from reanalysis showed a significant decrease during the fuel shortage of 7% and 6%, respectively. This study analyses the air quality and meteorological conditions during this period to evaluate whether these measures indirectly affected air quality in Mexico City. During the shortage, mean-ambient concentrations of nitric oxide (NO), nitrogen dioxide (NO2) and carbon monoxide (CO) were significantly lower than normal whereas levels of particulate matter (PM) were only modestly lower than usual. Daily-mean NO and CO had record-low anomalies of −10 ppb and −0.5 ppm from typical days, respectively. In contrast, ozone mean-levels were not significantly different than average. The percentage of days with PM mean concentrations above the World Health Organisation guidelines (5 and 19% for particles smaller than 2.5 and 10 μm, respectively) and the percentage of ozone 8-h rolling means above Mexican law (0.5%) were record lows. Meteorological factors, such as wind speed or the mixed-layer height were not significantly different than average. The anomalously low pollution levels were accentuated when each day was compared to days of similar flow patterns. This episode of better than usual air quality showcases how strategies addressing transport emissions could control air quality in Mexico City and highlights that improving ozone mean levels require comprehensive strategies that reduce emissions from all sectors.