Publications by Duncan Watson-Parris


Evaluation of global simulations of aerosol particle and cloud condensation nuclei number, with implications for cloud droplet formation

ATMOSPHERIC CHEMISTRY AND PHYSICS 19 (2019) 8591-8617

GS Fanourgakis, M Kanakidou, A Nenes, SE Bauer, T Bergman, KS Carslaw, A Grini, DS Hamilton, JS Johnson, VA Karydis, A Kirkevag, JK Kodros, U Lohmann, G Luo, R Makkonen, H Matsui, D Neubauer, JR Pierce, J Schmale, P Stier, K Tsigaridis, T van Noije, H Wang, D Watson-Parris, DM Westervelt, Y Yang, M Yoshioka, N Daskalakis, S Decesari, M Gysel-Beer, N Kalivitis, X Liu, NM Mahowald, S Myriokefalitakis, R Schrodner, M Sfakianaki, AP Tsimpidi, M Wu, F Yu


Analysis of the Atmospheric Water Budget for Elucidating the Spatial Scale of Precipitation Changes Under Climate Change.

Geophysical research letters 46 (2019) 10504-10511

G Dagan, P Stier, D Watson-Parris

Global mean precipitation changes due to climate change were previously shown to be relatively small and well constrained by the energy budget. However, local precipitation changes can be much more significant. In this paper we propose that for large enough scales, for which the water budget is closed (precipitation [P] roughly equals evaporation [E]), changes in P approach the small global mean value. However, for smaller scales, for which P and E are not necessarily equal and convergence of water vapor still plays a role, changes in P could be much larger due to dynamical contributions. Using 40 years of two reanalysis data sets, 39 Coupled Model Intercomparison Project Phase 5 (CMIP5) models and additional numerical simulations, we identify the scale of transition in the importance of the different terms in the water budget to precipitation to be ~3,500-4,000 km and demonstrate its relation to the spatial scale of precipitation changes under climate change.


tobac 1.2: towards a flexible framework for tracking and analysis of clouds in diverse datasets

GEOSCIENTIFIC MODEL DEVELOPMENT 12 (2019) 4551-4570

M Heikenfeld, PJ Marinescu, M Christensen, D Watson-Parris, F Senf, SC van den Heever, P Stier


The global aerosol-climate model ECHAM6.3-HAM2.3-Part 1: Aerosol evaluation

GEOSCIENTIFIC MODEL DEVELOPMENT 12 (2019) 1643-1677

I Tegen, D Neubauer, S Ferrachat, C Siegenthaler-Le Drian, I Bey, N Schutgens, P Stier, D Watson-Parris, T Stanelle, H Schmidt, S Rast, H Kokkola, M Schultz, S Schroeder, N Daskalakis, S Barthel, B Heinold, U Lohmann


Efficacy of Climate Forcings in PDRMIP Models

JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES (2019)

TB Richardson, PM Forster, CJ Smith, AC Maycock, T Wood, T Andrews, O Boucher, G Faluvegi, D Flaeschner, O Hodnebrog, M Kasoar, A Kirkevag, JF Larnarque, J Muelmenstaedt, G Myhre, D Olivie, RW Portmann, BH Samset, D Shawki, D Shindell, P Stier, T Takemura, A Voulgarakis, D Watson-Parris


Evaluation of global simulations of aerosol particle number and cloud condensation nuclei, and implications for cloud droplet formation

Atmospheric Chemistry and Physics Discussions European Geosciences Union (2019)

GS Fanourgakis, M Kanakidou, A Nenes, S Bauer, T Bergman, KS Carslaw, A Grini, DS Hamilton, JS Johnson, VA Karydis, A Kirkevag, JK Kodros, U Lohmann, G Luo, R Makkonen, H Matsui, D Neubauer, JR Pierce, J Schmale, PHILIP STIER, K Tsigaridis, T van Noije, H Wang, D WATSON-PARRIS, DM Westervelt, Y Yang, M Yoshioka, N Daskalakis, S Decesari, M Gysel Beer, N Kalivitis, X Liu, NM Mahowald, S Myriokefalitakis, R Schrödner, M Sfakianaki, AP Tsimpidi, M Wu, F Yu


Increased water vapour lifetime due to global warming

Atmospheric Chemistry and Physics Discussions European Geosciences Union (2019)

Ø Hodnebrog, G Myhre, BH Samset, K Alterskjær, T Andrews, O Boucher, G Faluvegi, D Fläschner, PM Forster, M Kasoar, A Kirkevåg, J-F Lamarque, D Olivié, D Shawki, TB Richardson, D Shindell, KP Shine, P Stier, T Takemura, A Voulgarakis, D Watson-Parris

The relationship between changes in integrated water vapour (IWV) and precipitation can be characterized by quantifying changes in atmospheric water vapour lifetime. Precipitation isotope ratios correlate with this lifetime, a relationship that helps understand dynamical processes and may lead to improved climate projections. We investigate how water vapour and its lifetime respond to different drivers of climate change, such as greenhouse gases and aerosols. Results from 11 global climate models have been used, based on simulations where CO2, methane, solar irradiance, black carbon (BC), and sulphate have been perturbed separately. A lifetime increase from 8 to 10 days is projected between 1986–2005 and 2081–2100, under a business-as-usual pathway. By disentangling contributions from individual climate drivers, we present a physical understanding of how global warming slows down the hydrological cycle, due to longer lifetime, but still amplifies the cycle due to stronger precipitation/evaporation fluxes. The feedback response of IWV to surface temperature change differs somewhat between drivers. Fast responses amplify these differences and lead to net changes in IWV per degree surface warming ranging from 6.4±0.9 %/K for sulphate to 9.8±2 %/K for BC. While BC is the driver with the strongest increase in IWV per degree surface warming, it is also the only driver with a reduction in precipitation per degree surface warming. Consequently, increases in BC aerosol concentrations yield the strongest slowdown of the hydrological cycle among the climate drivers studied, with a change in water vapour lifetime per degree surface warming of 1.1±0.4 days/K, compared to less than 0.5 days/K for the other climate drivers (CO2, methane, solar irradiance, sulphate).


Water vapour adjustments and responses differ between climate drivers

ATMOSPHERIC CHEMISTRY AND PHYSICS 19 (2019) 12887-12899

O Hodnebrog, G Myhre, BH Samset, K Alterskjaer, T Andrews, O Boucher, G Faluvegi, D Flaeschner, PM Forster, M Kasoar, A Kirkevag, J-F Lamarque, D Olivie, TB Richardson, D Shawki, D Shindell, KP Shine, P Stier, T Takemura, A Voulgarakis, D Watson-Parris


Contrasting Response of Precipitation to Aerosol Perturbation in the Tropics and Extratropics Explained by Energy Budget Considerations.

Geophysical research letters 46 (2019) 7828-7837

G Dagan, P Stier, D Watson-Parris

Precipitation plays a crucial role in the Earth's energy balance, the water cycle, and the global atmospheric circulation. Aerosols, by direct interaction with radiation and by serving as cloud condensation nuclei, may affect clouds and rain formation. This effect can be examined in terms of energetic constraints, that is, any aerosol-driven diabatic heating/cooling of the atmosphere will have to be balanced by changes in precipitation, radiative fluxes, or divergence of dry static energy. Using an aqua-planet general circulation model (GCM), we show that tropical and extratropical precipitation have contrasting responses to aerosol perturbations. This behavior can be explained by contrasting ability of the atmosphere to diverge excess dry static energy in the two different regions. It is shown that atmospheric heating in the tropics leads to large-scale thermally driven circulation and a large increase in precipitation, while the excess energy from heating in the extratropics is constrained due to the effect of the Coriolis force, causing the precipitation to decrease.


In situ constraints on the vertical distribution of global aerosol

ATMOSPHERIC CHEMISTRY AND PHYSICS 19 (2019) 11765-11790

D Watson-Parris, N Schutgens, C Reddington, KJ Pringle, D Liu, JD Allan, H Coe, KS Carslaw, P Stier


Understanding Rapid Adjustments to Diverse Forcing Agents.

Geophysical research letters 45 (2018) 12023-12031

CJ Smith, RJ Kramer, G Myhre, PM Forster, BJ Soden, T Andrews, O Boucher, G Faluvegi, D Fläschner, Ø Hodnebrog, M Kasoar, V Kharin, A Kirkevåg, J-F Lamarque, J Mülmenstädt, D Olivié, T Richardson, BH Samset, D Shindell, P Stier, T Takemura, A Voulgarakis, D Watson-Parris

Rapid adjustments are responses to forcing agents that cause a perturbation to the top of atmosphere energy budget but are uncoupled to changes in surface warming. Different mechanisms are responsible for these adjustments for a variety of climate drivers. These remain to be quantified in detail. It is shown that rapid adjustments reduce the effective radiative forcing (ERF) of black carbon by half of the instantaneous forcing, but for CO2 forcing, rapid adjustments increase ERF. Competing tropospheric adjustments for CO2 forcing are individually significant but sum to zero, such that the ERF equals the stratospherically adjusted radiative forcing, but this is not true for other forcing agents. Additional experiments of increase in the solar constant and increase in CH4 are used to show that a key factor of the rapid adjustment for an individual climate driver is changes in temperature in the upper troposphere and lower stratosphere.


Quantifying the Importance of Rapid Adjustments for Global Precipitation Changes.

Geophysical research letters 45 (2018) 11399-11405

G Myhre, RJ Kramer, CJ Smith, Ø Hodnebrog, P Forster, BJ Soden, BH Samset, CW Stjern, T Andrews, O Boucher, G Faluvegi, D Fläschner, M Kasoar, A Kirkevåg, J-F Lamarque, D Olivié, T Richardson, D Shindell, P Stier, T Takemura, A Voulgarakis, D Watson-Parris

Different climate drivers influence precipitation in different ways. Here we use radiative kernels to understand the influence of rapid adjustment processes on precipitation in climate models. Rapid adjustments are generally triggered by the initial heating or cooling of the atmosphere from an external climate driver. For precipitation changes, rapid adjustments due to changes in temperature, water vapor, and clouds are most important. In this study we have investigated five climate drivers (CO2, CH4, solar irradiance, black carbon, and sulfate aerosols). The fast precipitation responses to a doubling of CO2 and a 10-fold increase in black carbon are found to be similar, despite very different instantaneous changes in the radiative cooling, individual rapid adjustments, and sensible heating. The model diversity in rapid adjustments is smaller for the experiment involving an increase in the solar irradiance compared to the other climate driver perturbations, and this is also seen in the precipitation changes.


Short Black Carbon lifetime inferred from a global set of aircraft observations

NPJ CLIMATE AND ATMOSPHERIC SCIENCE 1 (2018) ARTN 31

MT Lund, BH Samset, RB Skeie, D Watson-Parris, JM Katich, JP Schwarz, B Weinzierl


On the Limits of CALIOP for Constraining Modeled Free Tropospheric Aerosol

GEOPHYSICAL RESEARCH LETTERS 45 (2018) 9260-9266

D Watson-Parris, N Schutgens, D Winker, SP Burton, RA Ferrare, P Stier


Community Intercomparison Suite (CIS) v1.4.0: a tool for intercomparing models and observations

GEOSCIENTIFIC MODEL DEVELOPMENT 9 (2016) 3093-3110

D Watson-Parris, N Schutgens, N Cook, Z Kipling, P Kershaw, E Gryspeerdt, B Lawrence, P Stier


Carrier Density Dependent Localization and Consequences for Efficiency Droop in InGaN/GaN Quantum Well Structures

JAPANESE JOURNAL OF APPLIED PHYSICS 52 (2013) UNSP 08JK10

TJ Badcock, S Hammersley, D Watson-Parris, P Dawson, MJ Godfrey, MJ Kappers, C McAleese, RA Oliver, CJ Humphreys


The consequences of high injected carrier densities on carrier localization and efficiency droop in InGaN/GaN quantum well structures

JOURNAL OF APPLIED PHYSICS 111 (2012) ARTN 083512

S Hammersley, D Watson-Parris, P Dawson, MJ Godfrey, TJ Badcock, MJ Kappers, C McAleese, RA Oliver, CJ Humphreys


Study of efficiency droop and carrier localisation in an InGaN/GaN quantum well structure

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 8, NO 7-8 8 (2011)

S Hammersley, TJ Badcock, D Watson-Parris, MJ Godfrey, P Dawson, MJ Kappers, CJ Humphreys, C Wetzel, A Khan


Carrier localization mechanisms in InGaN/GaN quantum wells

Physical Review B American Physical Society 83 (2011)

D Watson-Parris, MJ Godfrey, P Dawson, RA Oliver, MJ Galtrey, MJ Kappers, CJ Humphreys

Localization lengths of the electrons and holes in InGaN/GaN quantum wells have been calculated using numerical solutions of the effective mass Schrödinger equation. We have treated the distribution of indium atoms as random and found that the resultant fluctuations in alloy concentration can localize the carriers. By using a locally varying indium concentration function we have calculated the contribution to the potential energy of the carriers from band gap fluctuations, the deformation potential, and the spontaneous and piezoelectric fields. We have considered the effect of well width fluctuations and found that these contribute to electron localization, but not to hole localization. We also simulate low temperature photoluminescence spectra and find good agreement with experiment.


Energy landscape and carrier wave-functions in InGaN/GaN quantum wells

PHYSICA STATUS SOLIDI C: CURRENT TOPICS IN SOLID STATE PHYSICS, VOL 7, NO 7-8 7 (2010)

D Watson-Parris, MJ Godfrey, RA Oliver, P Dawson, MJ Galtrey, MJ Kappers, CJ Humphreys, SJ Park

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