‘Sure,’ acquiesced Dr Jones good-naturedly, and in less than a minute a big diagram from the USGS was up on the overhead, reminding the audience of what they may or may not have learned at school.
‘We can skip all the detail about volcanic steam, sublimation, desublimation and fog drip,’ Dr Jones informed them bracingly. ‘But it’s clear to see that what we have here is an ever-renewing system. Rain falls. It ends up in rivers and lakes, groundwater run-off and all the rest until eventually it reaches the oceans from where it evaporates, filling the air with water vapour. The water vapour becomes rainfall which goes into rivers, lakes and what have you, and the cycle starts all over.
‘But I guess when you guys were fourth-graders, your teachers probably told you that the water vapour was spread pretty evenly through the atmosphere. Well, nowadays we know it’s more complicated than that. The air up above our heads is actually full of streams. We can be absolutely certain of this now we have information from the Global Precipitation Measurement, or GPM, core observatory satellite that was launched back in 2014. The GPM mission was designed to build on the Tropical Rainfall Measuring Mission. That’s TRIMM to anyone into acronyms. TRIMM is also a joint mission between NASA and the Japan Aerospace Exploration Agency. It was launched in 1997 but only measures precipitation in the tropics. The GPM core observatory satellite has extended coverage from the Arctic Circle to the Antarctic Circle. And what both satellite systems are showing us at the moment is a stream — what we call an atmospheric river — of humid air forming over the Pacific Ocean with the potential to come right for us. You’ve all heard of the jet stream, I’m sure. There’s one up above us at the moment, about ten miles above us, in fact, right at the top of the troposphere. It’s three miles in diameter, give or take, and three thousand or so miles long. It’s a river of air that flows round and round the globe. It moves like a bat out of hell and anyone thinking of flying to Europe will probably get to ride along with it.
‘That’s just one stream, though it’s the best known. But there are others, much lower in the atmosphere. And they are effectively rivers of air that is so humid it is just on the point of precipitating. Unlike the jet stream, these atmospheric rivers can be hundreds of miles wide, but just like the jet stream they can be thousands of miles long. And also like the jet stream, they tend to move from west to east because of the way the Earth turns on its axis. And under certain circumstances they can blow in off the Pacific right over the West Coast here. Once every couple of centuries, in fact, on average.
‘Then all it takes is the elevation of something like the Sierra Nevada to push this incredibly humid air upwards and make the rain start pouring down along a storm front that can be as wide as the entire Californian coast. And it won’t stop coming down until the whole of that atmospheric river has gone over the top of us and dumped every last drop of moisture it contains on to our businesses, homes, families and loved ones.
‘Like I said, the stats show that we can expect one every couple of centuries. And it’s well past one hundred and fifty years since the last one, which means, by definition, that the odds are narrowing. And also because, like I said, our weather sats, TRIMM and GPM, are beginning to pick up what looks like an atmospheric river coming our way. Because we at the USGS and NOAA think there may be an ARkStorm due to hit us within the next seventy-two hours and stay right above us, raining fit to burst, for forty days after that,’ said Dr Jones. ‘Just like in the Bible. And that movie with Russell Crowe.’
FOUR
‘Is that what you were looking at, Richard?’ demanded Robin, shouting over the roaring of the Bell’s rotors, too impatient to wait for everyone to fit their headsets on. ‘When you were looking away to the west? An ARkStorm on the way in?’
‘I don’t know,’ answered Richard more quietly, his headset in place. ‘There was just something … But Doctor Jones said it was seventy-two hours out … Nic, can you ask your pilot to take us up as high as possible? We’re heading south-west back to the Long Beach docks anyway, and the higher we go the further I’ll be able to see out over the Pacific.’
‘Like you’re going to see more than one of the USGS satellites,’ said Nic, unsure whether to be incredulous or impressed. ‘That’s not forecasting, that’s witchcraft.’ But he shrugged and went forward to talk to the pilot. At once the chopper began to gain altitude and, as it did so, the vista all around it widened. Richard pressed the slightly broken aquiline jut of his nose against the starboard window, straining to see above the haze that cloaked the grey city blocks away out past the cost and over the sullen grey-green of the ocean. His mind began to fill with the rest of what Dr Jones had told the Chamber of Commerce. The governor, slipping into the decisive mode of a couple of his more dramatic predecessors, Regan and Schwarzenegger, had already called in the National Guard. And the USGS had backed him forcefully enough to alarm the president and the power brokers up on Capitol Hill. Containers full of medical supplies, emergency rations, heating and clothing were on the way, apparently. Everything from chemical toilets to mobile hospitals, all packed in containers and loaded into — or on to — every form of transport available. Preparing for the worst without panicking the populace.
There was an evacuation plan that would slip into place when the rain began to fall — but not until then. This wasn’t going to be like an earthquake — total destruction in a couple of minutes, then aftershocks, fires and so forth. A city and its infrastructure wasn’t going to be reduced to rubble in little more than a heartbeat. It wasn’t going to be Mount St Helen’s — or Pompeii and Herculaneum. Folks would get wet as they moved. Soaked and shaken — especially if the storm fronts were powerful. He remembered how it had been in the south of England in February 2014 with hurricane-force winds in the Western Approaches, along the south coast and up through St George’s Channel and over the Isle of Anglesey. But if push came to shove the vast majority of Californians would have days, possibly weeks before things became impossible.
The only exceptions would be the unfortunate people living along the western, coast-facing slopes of the Sierra Nevada, for those steep surfaces would begin to wash away in the first few hours, taking everything and everyone with them. He closed his eyes for a moment, summoning up a sketchy map from the depths of his near-photographic memory. There would be more towns than Wishon inundated by Bass Lake and the offspring it would all too swiftly spawn. North Fork would be among the first, he supposed, washed down towards Yosemite, lock, stock and barrel …
But at this point in his darkening thoughts, Richard’s concentration was disturbed. ‘Oh my God,’ Robin said to Nic. ‘What in heaven’s name is that? It looks like something out of Mars Attacks!’
‘The Graf Zeppelin meets the Starship Enterprise, perhaps,’ Nic allowed.
The mention of the Enterprise was too much for Richard, a card-carrying Trekkie. ‘What is it?’ he asked, blinking his eyes wide and looking away from the darkening distance westwards. Robin and Nic were on the inland side of the chopper, looking south-eastwards towards Anaheim — another of the west-slope areas that might find itself in the first firing line, he thought as he crossed to crouch beside them. And there, above the grey haze of morning, framed against the distant sage of the Santa Ana Mountains, was an airship. Looking like the Goodyear blimp crossed with something out of the Terminator movies, it gleamed silver in the clearer inland air, aptly enough seeming to be sailing just above the historic settlement of Silverado itself. Its frame was too flat for a cigar shape, and as it moved through the air with slow majesty its silhouette seemed to flatten further still, almost like a flying saucer. Richard could see what Robin meant about Mars Attacks!, not to mention The War of the Worlds and The Day The Earth Stood Still. Then it lengthened again and tall tail fins became apparent. Suddenly it looked more like a submarine. One of the sleek new Virginia-class boats — given a slightly flattened hull. ‘What sort of size is it?’ whispered Richard, awed.