The Maritime Continent (MC) of Southeast Asia, comprising the archipelago of islands from the Malay Peninsula through Indonesian New Guinea and the Philippines, hosts some of the world’s most complex aerosol, cloud, and coupled ocean–terrestrial–atmospheric systems. With its steep topography situated in the Pacific warm pool, the MC is an important contributor to Earth’s moisture, energy, and vertical transport budgets far outside its tropical latitude range (e.g., Ramage 1968; Jin and Hoskins 1995; Neale and Slingo 2003; Carminati et al. 2014). High levels of pollution and biomass burning emissions contrast with natural marine and biogenic aerosol sources. Burning for agriculture and urbanization occurs at significant rates (Miettinen et al. 2016). These burning emissions are strongly tied to precipitation anomalies associated with numerous interseasonal and intraseasonal cycles (Field and Shen 2008; Reid et al. 2012, 2013; Field et al. 2016) and a nonlinear hydrological response (Taufik et al. 2017). The region further includes significant anthropogenic emissions from heavy industry, mobile sources, and biofuel (e.g., Balasubramanian et al. 2003; Lee et al. 2019; Chen et al. 2020). The resulting regional-scale air quality events are among the worst in the world with adverse health outcomes and economic feedback (e.g., Kim et al. 2015; Crippa et al. 2016; Koplitz et al. 2016, 2017; Lee et al. 2018, 2019). Increasing emissions coincide with climatic change in temperature and rainfall within a region already vulnerable to weather extremes (e.g., Endo et al. 2009; Yusef and Francisco 2009; IPCC 2013, 2014; Deni et al. 2010; Cruz et al. 2013; Cinco et al. 2014; Villafuerte et al. 2014; Olaguera et al. 2018; Bagtasa 2020).
Clouds within the MC exist in a spectrum of pristine through highly polluted regimes and likely demonstrate aerosol particle, microphysics, precipitation, and radiation interdependencies. Observational evidence suggests higher aerosol loadings result in 1) enhanced warm cloud albedo in Southeast Asia (Sorooshian et al. 2009, 2013; Ross et al. 2018) due to reduced droplet size, through the Twomey effect (Twomey 1974, 1977); 2) indicators of aerosol-related storm invigoration have been observed through enhanced lightning (e.g., Yuan et al. 2011; Thornton et al. 2017); and 3) suppressed warm rain and enhanced deep-convection-related precipitation processes (e.g., Rosenfeld and Lensky 1998; Rosenfeld 1999). While it is unclear how aerosol impacts differ in terrestrial versus maritime environments, we expect findings from other regions and modeling studies to have some applicability to the MC. These include a host of aerosol-induced micro- and macrophysical changes in clouds (e.g., Tao et al. 2012; Dey et al. 2011), such as delays in warm rain formation (Berg et al. 2008) and congestus and overall storm invigoration (e.g., Lyons et al. 1998; Wang et al. 2009; Storer et al. 2014). Modeling studies are largely consistent in warm-phase cloud processes, but less so as ice nucleation begins to take hold (Khain et al. 2005; van den Heever et al. 2006; Saleeby et al. 2010; Cotton et al. 2012; Fan et al. 2013; Grant and van den Heever 2015; Sheffield et al. 2015; Mace and Abernathy 2016; Gryspeerdt et al. 2017). At the same time, radiation perturbations by particles feed back into atmospheric stability and cloud formation (Ackerman et al. 2000; Sokolowsky et al. 2022). In sum, aerosol particle impacts on cloud processes are coupled to aerosol life cycle, the radiative budget, and feedback to cloud microphysical and dynamical processes.
The National Aeronautics and Space Administration (NASA) Cloud, Aerosol and Monsoon Processes Philippines Experiment (CAMP2Ex), conducted from Clark International Airport, Philippines, with its 25 August–5 October 2019 intensive operations period, worked to deconvolve interlaced aerosol, cloud, and radiation processes to isolate the role of aerosol particles within Southeast Asia’s southeast monsoon system. To document the mission and promote its use to a broad interdisciplinary community, this paper provides a summary of CAMP2Ex, a demonstration of some of the technology developed to meet its scientific goals, and the mission’s assets, experienced environments, and early scientific findings. To promote the use of CAMP2Ex data, extensive supplemental material is also provided for the measured environment, the instrument payloads/performances, and remote sensing and modeling components (supplemental sections S.1, S.2, and S.3, respectively). CAMP2Ex was organized around compositional, convective, and radiative focus areas with associated in situ, modeling, and remote sensing technology efforts investigating warm- and mixed-phase clouds, such as fair weather cumulus, congestus, and altocumulus, as well as their organization and proclivity to develop into deeper convection. NASA’s P-3 aircraft, Stratton Park Engineering Company’s (SPEC) Learjet 35 aircraft, a Manila Observatory ground site, and partners including the Office of Naval Research (ONR) Propagation of Intraseasonal Tropical Oscillations (PISTON; Sobel et al. 2021) R/V Sally Ride research cruise and those involved in the Years of the Maritime Continent (Yoneyama and Zhang 2020), made useful observations. CAMP2Ex promoted not only interdisciplinary observations, but new informatics technologies to fuse field observations with satellite remote sensing and modeling efforts to holistically examine the monsoon system. CAMP2Ex supports the next generation of Earth-observing systems including a host of the latest geostationary sensors such as on Himawari-8 (Bessho et al. 2016) and NASA’s developing Atmosphere Observing System (AOS).